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PBW1300lC0O4845 We assure cempi amze with US Government mpyright iaw Permissian in dupiicate any materials covered by mpyright Eaw has ham sacumcf GEOLOGY 470570 ENGINEERING GEOLOGY Winter Quarter 2013 l Professor Dr Scott Burns 2 Office Cramer Hall l7R 3 Telephone 503 7253389 4 Office Hours MWF 900l000 and by apt 5 Book for Course Johnson and DeGraff Principles of Eng mxxinq Geology Wiley l988 I have a lab manual that is out of print and I can print the labs for a small fee or you can download them from D2L 6 Important Dates 7 8 9 l0 a Midterm Feb 6 20l3 b Backyard project due Feb ll 20l3 c Graduate Project presentation Mar l5 20l3 c Graduate project due Mar l9 20l3 d Final Exam Mar l7 20l3 Grades Undergraduates Graduates a Midterm 30 20 b Backyard Project l5 l0 c Final Exam 35 25 d Graduate Project 20 e Graduate Present l0 f Lab Problem Sets 20 l5 Graduate Students All students taking the class for graduate credit Geology 570 will do a special project in addition to the rest of the work in the class This can be a field project using the field principles learned in the class It can be a laboratory project based on engineering geology principles can be an indepth report on an engineering geology investigation This year there will be projects available at Camp Arrowhead These topics must be cleared with the instructor by January 23rd They will be presented in class on March l5th and the written project will be handed in the l7th of March It Backyard Project All students will do an engineering geology investigation of where you live I will hand out the exact information soon on this It will entail reading a soil survey topo map and a geologic map You will also have to run Atterberg Limits tests on the soils It will be fun These will be due February ll 20l3 530645 PM CH Sl7 Sec 002 Friday 35 PM Meeting times Monday and Wednesday CRN 45835 45833 amp 45834 45832 ll Laboratory The lab is required as part of the class It will meet on Friday from 300500 PM Weekly problem sets will be assigned and handed in the next Friday Some of the labs will be in the field LIST OF TOPICS IN ORDER READINGS I Introduction I lecture l39 a Introduction to course b Geology amp Mechanics Fundamentals 2 Investigation Fundamentals l lecture 4074 a Role of Engineering Geologist b Elements of an investigation c Types of investigations d Professional practices e Report writing and record taking 3 Soils Soil Mechanics amp Uses 3 lectures 75I25 a Description for engineering purposes b Classification of soils c Engineering properties Expansive soils d Use of the classifications e Use of soil surveys 4 Rocks Rock MechanicsUses 3 lectures l262l2 a Intact rocks b Rock masses and discontinuities c Engineering classification of rocks 5 Construction uses of rocks I lecture 363392 a Aggregates amp Riprap 6 Subsurface water I lecture 2l3240 aEngineering significance b Controls of groundwater 7 Instrumentation l lecture 24l266 a Instrument components b Instrument types and applications 8 Exploration l lecture 267362 a Maps b Remote Sensing c Subsurface exploration 9 Earth Processes amp Terrain Models 4 lectures 393490 a Prediction Vegetation and Wetlands b Tectonic Volcanic Shoreline River amp Ice Processes c Slope Stability Rock and Soil Slopes d UBC and Grading l0 Leadership in Engineering Geology Field l lecture Notes are available on D2L and at Clean Copy 1720 SW Broadway DATE 1 11113 2 11813 3 12513 4 2113 5 2813 6 21513 7 21513 8 22213 9 3813 10 31413 G470570 ENGINEERING GEOLOGY LAB AND FIELD TRIP SCHEDULE WINTER QUARTER 2013 ACTIVITY PROBLEMS DUE NEXT WEEK Review of Mechanics CH S17 Ex 2 Ex 3 Plan View and Cross Section of Slide Field Lab Field Developed Cross Section Drive Probe Portland Zoo Lab Atterberg limits soil characterization Ex 10 Ex 11 Ex 12 of samples taken last week CH S17 13 Soil Compressibility soil sheet Ex 13 Rock mechanics Ex 4 EX 6 Ex 7 Rock Slope Stability torvane penetrometer Ex 8 Ex 9 Schmidt Hammer Scott gone Field Trip Portland Hills Landslides EX 14 Computer Lab LISA DLISA XSTABL Handout in class See page Characteristics CH S17 Ex 16 Scott gone Graduate Student Presentations CH S17 Assignments are due the following week at the beginning of class Introduction Lecture Engineering Geology Chapter 1 1 What is engineering geology A De nition application of geologic fundamentals to civil engineering 1 Applied science B Geology Study of earth s materials A Study of processes of earth surfacebelow B Study of earth s history C Civil Engineer a person who designs and builds public works 1 Structural engineer design construction planning monitoring of buildings 2 Environmental sewage water supplies garbage wastes 3 Geotechnical soils rocks foundations 4 Transportation roads airports railroads etc D Civil engineer uses above concepts to predict and for practical uses 1 Areas of constraint affect design construction maintenance 2 Risks dams 3 Location of sites 4 Economics What will increase costs shale 1 What will decrease costs granite 5 Forecasts future events like oods landslides 6 Very important can t be wrong if wrong lose lives and money 1 Civil engineer scientist denied privilege of being wrong E Engineering geologist translator and predictor for the civil engineer 2 Geology fundamentals JD 119 A Rock vs soil 1 Rock geol natural occurring material of 1 minerals 2 Rock engin hard compact natural material 3 Soil geol supports life weathering products and OM 4 Soil engin separated by agitation in water ie shovel into it B Igneous rocks 1 Classification p4 sizes and minerals same names 2 Crystal size strengths 3 Sizes of bodies extrusives 4 Pyroclasticstuffs holes for compression erosion 5 Dikessills problem areas 6 J ointing C Sedimentary Rocks 1 Classification p8 same names 2 Wide range of physical properties and extent 3 Bedding slope stability and discontinuities 4 Cement differ particle size clay D Metamorphic rocks 1 Classification p 10 same names 2 Whether foliation E Weathering 1 Altering of engineering properties F G 2 Also tells of weathering of structure buildings you build 3 Water freezing where calcite faults hydr alt 4 Stratigraphy discontinuities and diff Strength layers for models 5 Hydrogeology how geology affects all of water movement Geomorphology landforms 1517 1 Sediment characteristics strength 2 Weathering stability 3 Drainage pattern A Low density permeable or karst B High density impermeable 4 Slides hummocky Structure 1719 1 Faults folds discontinuities 2 Use maps to predict problems and faults A Eisenhower Tunnel W 9 2 COMPARATIVE FIELD OF GEOLOGY ENGINEERING GEOLOGY AND ENGINEERING GEOLOGY ENGINEERING GEOLOGY CIVIL ENGINEER Interpret Interpret and predict calculate and design typical basic training areas general geology statics historical geology Zgdynamics I mineralogy E materials petrology amp petrog I surveying sedimentary pet fluid mechanics geomorphology engineering geol structure design structural geol ground water hydrol hydraulics stratigraphy geophysics paleontology advanced geomorphology regional synthesis geophysics geochemistry both engineering geology and geotechnical engineer soil mechanics rock mechanics foundation design Typical applications Geology Engineering Geology Engineer Mapping regional planning data sampling sampling site selection testing classifying reconnaissance data measurement identification site overview surveying mine evaluation hazard evaluation analysis hydrothermal erosion structure design terrain history flooding Process analysis faulting Structural earthquake Stratigraphic volcanic risk coastal erosion site specific study landforms Stratigraphic units soil and rock units subsurface investigation testing and analysis GL4 xG I1 4quot T F 1 1 APPLICATION OF GEOLOGY ENGINEERING GEOLOGY amp ENGINEERING ORS 672505 4 quotGeologist means a person engaged in the practice of geologyquot 6 quotquotGeologyquot refers to that science which treats of the earth in general investigation of the earth39s crust and the rocks and other materials which compose it and the applied science of utilizing knowledge of the earth and its constituent rocks minerals liquids gasses and other materials for the benefit of mankindquot 80920006 1 quotA geologist shall undertake professional services or render expert opinion only when qualified by training or experience in the technical areas involvedquot 2 quotWhen serving as EH1 expert or technical witness before a court commission or other tribunal a geologist shall express only those opinions founded upon adequate professional knowledge of the matters at issuequot REGISTERED GEOLOGIST Geological input is most ul where geologic terrains must be understood to preserve safetyh ality of land use ORS 672505 7 quotPublic practice of geologyquot means the performance of geological service or work for the general public This includes consultation investigation surveys evaluation planningy mapping and inspection of geological work in which the performance is related to public welfare orquot safeguarding of life health property and the environment except as specifically exempted by ORS 672505 to 672705 Types of geologic investigations PERMITTED NON civil engineering works related Geologic Mapping Soil Rock and Hydrology investigations Mineral investigations Economic evaluations of geologic materials Geothermal Legal work not related to civil engineering works Types of work NOT PERMITTED Safety and engineering design evaluations for hire by public Hazard evaluationfaults earthquakes floods erosion volcanicetc Engineering design recommendations Land use planning evaluation relating to suitability and limitations of areas Opinions on safety and suitability of engineering projects or land use planning I cu E 0 ca m if1 2 vh A 5 M 4 quot r39 REGISREEEBTEEEDOGESJZOEISHI EHIIEBENEERINEEBEISIGOGEOBEETIEEEETECDEATION ORS 772505 3 quotEngineering geologistquot means 21 person who applies geologic data principles and interpretation to naturally occurring materials so that geologic factors affecting planning design construction and maintenance of civil engineering works are properly recognised and utilized Typical engineering geologic investigations All work permitted to a REGISTERED GEOLOGIST Plus Land use planning to determine suitability and limitations of engineering projects and land use Site selection investigations and evaluations Hazard investigation Landslide Flood Erosion River management Shoreline process investigation Earthquake shaking Fault capability Volcanic processes Subsidence solution expansive soil etc Resource evaluation Sand and gravel rock supplies soil and fill material water supply water contamination Natural resource evaluation Geologic environments of significant value Wetlands evaluation Engineering project evaluation foundations slope stability cut and fill excavations tunnel dams canals development planning waste disposal coasts and harbors roads and airfields bridges parks recreation and habitat etc Specific skills abilities tools and experience may be necessary for each of the types of activities CEG EXAMINATION BLUEPRINT INITIAL GEOLOGIC MODEL DEVELOPMENT application of air photo interpretations of geologic contacts structural geomorphic and cultural features geologic topographic and preliminary alignment maps geologic constraints and hazards and proposed grading plans and cross sections in the development of engineering geologic models SURFACE INVESTIGATIONS reconnaissance practices measuring discontinuities relative stability of materials field measurements prediction of material distribution uniformity continuity and quality earthquake related effects field classification of soil and rock samples for engineering properties SUBSURFACE INVESTIGATIONS development of exploration programs methods and tests methods of installing and monitoring soilrock instrumentation sample storage and protection exploration logging HYDROGEOLOGIC INVESTIGATIONS aquifer characterization aquifer tests hydrogeologic modeling dewatering and drainage methods and evaluation seepage control water sample collection LABORATORY STUDIES index and strength parameter testing of soil and rock laboratory testing program interpretation and uses of laboratory results GEOLOGIC MODEL REFINEMENT AND ANALYSIS use of genesis and history to predict occurrence and performance of materials use of mathematical and graphical methods to analyze problems such as those related to slope Stability foundations and surface and subsurface waters analysis of discontinuity data methods used to establish earthquake risk developing groundwater supplies use of refined geologic models to analyze and predict the behavior of earth material DESIGN RECOMMENDATIONS application of analysis results and the refined geologic model to the construction of foundations slopes erosion mitigation measures excavations and embankments the infrastructure and sanitary landfills the development of groundwater and well design earth material sources and coastalshoreline areas and the establishment of earthquake risk POST INVESTIGATION AND ANALYSIS ACTIVITIES construction observation post construction monitoring PROFESSIONAL PRACTICES expert witness administrative rules and statutes OAR amp ORSI liability exposure contract development and administration ethics BI G470I570 MECHANICS FUNDAMENTALS 1 S39l39RESS FORCEIAREA PRESSURE EXTERNAL LOAD THAT WORKS ON SOIL AND ROCK EXTERNAL LOAD A psi POUNDSISQUARE INCH ENGLISH B ces DYNEICM2 c SI PASCALS NEWTONSIM2 mpa MILLION D BARs 987 ATMOSPHERES 145 PSI 2 STRAIN DEFORMA39l39lONIDlSTOR139lON OF MATERIAL FROM STRESS EPSILON e ELONGATION A DEFORMATION CHARACTERISTICS 1 ELASTIC COMPLETELY RECOVERED A UNIFORM ROCKS N0 DENSIFICATION N0 PROGRESSIVE FAILURE B SLOPE VARIES CALLED MODLILUS OF ELAS139ClTY 1 STEEP quotSTlFFquot 2 LOW ANGLE quotWEAKquot c SUDDEN FAILURE No FOREWARNING so cAN HAVE ROCK BLIRSTS 2 PLASTIC PERMANENTLY DEFORMED sTREss EXCEEDS YIELD POINT OF MATERIAL A MOST COMMON WITH PORE DENSIFICATION 3 PLAS139lCELASTIC A DENSIFICATION OF PORES AT BEGINNING 4 ELASTICPLASTIC MIXED COMPOSITION SO WEAKER FAIL EARLIEST GRADUAL FAILURE G470I570 COMPONENTS OF AN EXCELLENT INVESTIGATION 1 PREREQUISITES OF A GOOD INVESTIGATION A COMPETENT GEOLOGIsT SKILLS LISTED IN cHAP 1 1 REGISTRATION sTATE EXAM GIT RG cEG B ABILITY TO TRANsLATE GEOLOGY FOR CIVIL ENGINEER 1 sTREss ENGINEERING PROPERTIEs OF MATTER 2 JOINTSIDEGREES OF WEATHERINGISTRENGTHS vs AGE MINERAL CONTENT DEP ENVIRONMENT FOSSILS c sOuND JUDGEMENT AND ABILITY TO MAKE DECISIONS 1 STRESS THE IAcTs 2 LINDERSTAND POLITICS AND AIMs OF PROJECT 3 uNDERsTAND TIME AND MONEY IAcTOR 4 LEVELHEADED TEMPERAMENT TAcT AND PRAcTIcALITY TOUGH JOB BECAUSE cLIENTs HATE You MORE so IN ENVIRONMENTAL 5 cOMMuNIcATION Is THE KEY 2 ELEMENTS OF THE lNVES139lGATON A FORMULATING THE INVESTIGATION 1 IDENTIFICATION OF QUESTlONS A MAIN ONE EX SUITABLE FOR BYPASS B SECONDARY sPRINGs sLOPE STABILITY 2 SCOPE OF INVESTIGATION A SIzE OF AREA B TIME DEADLINE 3 MoNEY AVAILABLE c WHEN FIELD 39l39lME SUMMER oR WINTER WINTER IS GREAT FOR LANDSLIDESI D HOW DETAILED FED AND STATE REGS 1 COLLECT OLD REPoRTS B CONTRACT wRITTEN DOCLIMENT oUTLINES DUTIES OF WORK IEES coNSTRAINTS ScoPE 1 TYPES USUALLY SUBMIT PRoPoSAL amp BID A IIxED FEE coST AND ovERHEAD B coST PLUS FIXED FEE c coST PLUS PERcENT OF coSTS IEES D coST PLUS PREMIUM FEE BASED oN coST SAVINGS 2 UNREALISTIC coNTRAcTS LEAD TO DELAYS coST ovERRUNS AND coURT BATTLES A BEWARE OF LOW BIDS WITH CHANGE ORDERS c DATA COLLECTION 1 OFFICE STUDY A JOURNALS MAPS ETC BEST TO HAVE OFFICE CLOSE TO UNIVERSITY B SoIL SURVEYS OF SITE C UNPUBLISHED REPORTS DOGAMI GOV 1 GEOTIMES EACH YEAR LIST OF ADDRESSES OF AGENCIES 2 PROPRIETARY DATA D AERIAL PHOTOS amp REMOTE SENSING DATA E MAPS TOPO amp GEOLOGICAL F RESULT WORKING HYPOTHESES BEFORE YOU GET TO THE FIELD 2 FIELD DATA COLLECTION A SURFACE EXPLORATION ALL ONTO TOPO SPRINGS LANDSLIDES SOILS STRIKES DIPS B SUBSURFACE EXPLORATION 1 DIRECT PITS TRENCHES CORES 2 INDIRECT GEOPHYSICAL GPR MAGNETIC REFLECTION SEISMIC 3 RESULTS GEO PROFILES ISOPACHS C SAMPLINGquot TESTING 1 IN SITU SPT SOIL PH ETC 2 IN LABO ROCKISOIL STRENGTH D DOCUMENTATION 1 WRITE DOWN EVERYTHING NOTES 2 USED FOR BILLING 3 WHEN WHERE INSTRUMENTS SETTINGS LOGS SEE P 51 E NOTES SHOULD INCLUDE ROCKS SOILS GROUNDWATER STRUCTURE SLOPE FAILURES HAZARDS D ANALYSIS AND INTERPRETATION OF DATA 1 REDUCE DATA TO TABLES PROFILES MAPS 2 EXCESS DATA INTO APPENDIX OF REPORT 3 ALWAYS THINK MAP REVEALS SO MUCH 4 USE STATISTICS USE CORRELATIONS DISTRIBUTION STATISTICS ETC E COMMUNICATION WRITTEN AND ORAL REPORT 1 WHO IS AUDIENCE MANAGER BOARD EPA A LEARN THEIR FORMAT SEE 55 2 EFFECTIVE COMMUNICATIONS A HAVE EFFECTIVE ABSTRACT OR EXECUTIVE SLIMMARY LOTS OF PHOTOS FIGURES MAPS B LETTER OF TRANSMITTAL REPORT BEING TRANSMITTED AUTHORIZATION FOR DOING WORK OFFER TO CLARIFY ANY PART C PREFACTORY MATERIAL TITLE PAGE ABSTRACT TABLE OF CONTENTS D BODY OF REPORT 1 INTRODUCTION SCOPE 2 INVESTIGATION METHODS 8 CHRONOLOGY 3 RESULTS 4 DISCUSSION VALIDITY AND ACCURACY 5 CONCLUSIONS 6 REFERENCES 3 APPENDIx F MONITOR AFTER REPORT AND DURING CONSTRUCT0N PUT INTO cOST ESTIMATE 3 TYPES OF INVESTIGATIONS A REGIONAL STUDIES LARGE AREAS 1 MAINLY FOR LAND 3 RESOLIRCE MANAGEMENT 3 PLANNING wHERE ARE GEOHAZARDS RESOURcES LACKS DETAIL FOR DESIGN INVENTORIES USE GIS SEE P 61 2 RANKING OF SITES B SITE INVESTIGATIONS SMALL AREAS 1 GEO INFORMATION THAT AIIEcTS DESIGN AND cONSTRUcTION OF A PARTICULAR PROJECT GOV REGULATIONS WHAT TO ExPEcT DURING CONSTRUCTION cHANGES IN DESIGN cRITERIA cAN cOSTS BE KEPT DOWN 2 PRELIMINARY STUDY FIRST IS SITE SUITABLE 3 DETAILED INVESTIGATION FOR SOILIROCK INFO FOR THE DESIGN A FOR BUILDING A ROAD WET AREAS FOR DRAINAGE STREAMS FOR BRIDGES ROCK OUTCROPS FOR BLASTING SITES FOR FILL LANDSLIDES SPRINGS FOR CULVERTS 4 IMPLEMENTATION STUDY DURING CONSTRUCTION IMPORTANT FOR CHANGE ORDERS LOOK FOR FAULTS INSURES COMPLIANCE MAKES BETTER GEOLOGIC MAP COMPLETION WELLS IF MONITOR AFTER 4 PROFESSIONAL PRACTICES ETHICS A GENERAL MORAL RESPONSIBLE INTEGRITY B RELATION TO PUBLIC NOT SENSATIONAL NO INTEREST IN PROPERTY MUST KNOW WHY REPORT BEING DONE ONE SHALL NOT LIE C RELATION TO CLIENT PROTECT INTEREST OF CLIENT RESIGN IF CONFLICT OF INTEREST KEEP INFO IN CONFIDENCE D RELATION TO OTHER MEMBERS OF PROFESSION NO INJURY TO OTHERS NO PLAGIARISM COOPERATE WITH OTHERS G470570 ENGINEERING GEOLOGY REPORTS IN OREGON 1 GENERAL INFORMATION GOES INTO INTRO METHODS BACKGROUND INFORMATION A CLIENT B GEOLOGISTS DATES C LOCATION OF SITE amp REGIONAL GEOGRAPHY REGIONAL GEOLOGY TOPOGRAPHY DRAINAGE D LEVEL OF STUDY FEASIBILITY PRELIM FINAL E EXPOSURES F REFERENCES G LOCATIONS OF TESTING HOLES PITS TRENCHES H METHODS LAB AND FIELD I DISCLOSURE OF GEOLOGIST39S FINANCIAL INTEREST J SIGNATURE AND SEAL OF REGISTERED GEOLOGIST 2 GEOLOGIC MAPPING AND INVESTIGATION A GEOLOGIC MAP AT SUITABLE SCALE OF SITE AND APPROPRIATE ADJACENT SITES ON GOOD BASE B CROSS SECTIONS TO SHOW SUBSURFACE 3 GEOLOGIC DESCRIPTIONS A BEDROCK ROCK TYPE AGES NAMES THICKNESS PHYSICAL CHARACTERISTICS WEATHERING ZONES ENGINEERING GEOLOGY B STRUCTURE STRATIFICATION FAULTS DISCONTINUITIES FOLDS FOLIATION C SURFICIAL DEPOSITS AGES THICKNESS ENGINEERING CHARACTERISTICS EXPANSIVE CLAYS amp PEATS D HYDROLOGYSURFACE DRAINAGE SUBSURFACE FLOW DEPTHS TO GROUNDWATER SPRINGS AQUIFERS RECHARGE AND DISCHARGE AREAS WATER TABLE FLUCTUATIONS E SEISMIC CONSIDERATIONS SIZE FREQUENCY amp LOCATION OF QUAKES SURFACE RUPTURE POTENTIAL GROUND MOTION LIQUEFACTION LANDSLIDES 4 ASSESSMENT OF GEOLOGIC FACTORS A GENERAL SUITABILITY OF PROPOSED LAND USE TO GEOLOGIC CONDITIONS AVOID THESE AREAS MITIGATION ALTERNATIVES STABLE SITES HAZARDS B IDENTIFICATION amp EXTENT OF KNOW GEOL HAZARDS C RECOMMENDATIONS FOR SITE GRADING AVOIDANCE OF LANDSLIDES EXCAVATION CONSIDERATIONS PROPOSED FILL EFFECTS FILL FROM SITE D DRAINAGE CONSIDERATIONS PROTECTION FROM INUNDATION WAVE EROSION POTENTIAL SEPTIC SYSTEMS POTENTIAL EROSION E LIMITATIONS OF STUDY FUTURE BORINGS FUTURE EXPLORATIONS LONG TERM MONITORING 5 RECOMMENDED TECHNIQUES A GLQ SYSTEM OF KEATON B USC FOR SOILS C UNIFIED ROCK CLASSIFICATION WILLIAMS G47053970 SOIL MECHANICS READ CHAPTER 3 3975 125 1 INTRODUCTION A ENGINEERING SOIL MINERAL MATTER THAT LACKS STRENGTH MAY INCLUDE SAPROLITE B ROLE OF SOIL IN ENGINEERING 1 BUILDING MATERIAL DAMS LEVEES SLOPES 2 STRUCTURES FOUNDED IN IT 3 SLOPES ADJACENT TO A STRUCTURE 2 DESCRIBING SOIL FOR ENGINEERING PURPOSES A COLOR TELLS STATE OF DRAINAGE 1 REDORANGE WELLDRAINED 2 GRAY POORLY DRAINED 39 Fe REDUCED 3 REDGRAY MOTTLES REDOXYMORPHIC FEATURES FLUCTUATING WATER TABLE AND POORLY DRAINED 4 USE MUNSELL COLOR BOOK B pH SOIL REACTION ACIDBASE 1 CAN DO IN FIELD WITH TAPES 2 BEST IN LAB DO 11 WATER 3 ACIDIC CORRODES STEEL E AFFECTS CEMENT C BULK DENSITY MAINLY USED BY GEOLOGISTS 1 DRY WEIGHTUNIT VOLUME 2 gcc USE TUBE OF KNOWN VOLUME D UNIT WEIGHT SIMILAR TO BULK DENSITY BUT CE39S 1 WEIGHT OF MATERIALVOLUME OF MATERIAL 2 MOIST UNIT WEIGHT VOIDS FILLED WITH WATER AND AIR 3 DRY UNIT WEIGHT VOIDS FILLED WITH AIR 4 SATURATED UNIT WEIGHT VOIDS FILLED WITH WATER 5 TO CONVERT BULK DENSITY TO UNIT WEIGHT MULTIPLY BY 624 LBSFT3 6 CHART 7397 Vt Vv Va vw Vs ws Ww Wt E SPECIFIC GRAVITY GS DRY WEIGHT CUBIC FTWEIGHT OF CUBIC FT OF39WATER 1 DIVIDE BY 624 2 QUARTZ 267 3 MOST SOIL 10 4 FRAGIPAN 20 F POROSITY VVVt X 100 n 1 RANGES 0 100 SAND 4050 SEE p80 G VOID RATIO e VvVs n1n 1 624 Gsunit weight dry 1 2 RANGES 0 TO INFINITY DENSE ABOUT 3 LOOSE AT 1 H DEGREE OF SATURATION S PROPORTION OF VOID SPACE IN SOIL MASS CONTAINING WATER 1 S vwvv X 100 39W Gse MOISTURE CONTENT SPECGRAVVOID RATIO 2 RANGE 0 100 I MOISTURE CONTENT W WwWs x 100 WtWsWs x100 1 RANGE 0 100 J GRADATION PASSING 1 WELLGRADEDPOORLY SORTED 2 POORLY GRADED WELL SORTED 3 GAP OR SKIP GRADED 4 GEOLOGISTS GRADING CURVE CUMULATIVE K BOUNDARIES GEOL ENGIN SOILS BOULDERS 25 6mm 305mm COBBLES 64m 76mm 76m PEBBLES 2mm 10 475 4 2mm SAND 062 230 074 200 050 250 SILT 002 005 002 CLAY L COHESIVE SOILS FINEGRAINED AND DON39T DISAGGREGATE M ATTERBERG LIMITS A PLASTIC LIMIT WHEN DRY SOIL IS WET ENOUGH TO AGGREGATE MAKE WORMS PL B LIQUID LIMIT WHEN SOILS FLOWS MACHINE LL C PLASTICITY INDEX PI LL PL N ACTIVITY PI CLAY A LOW KAOLINITE LOTS OF CA NA 3 B HIGH SMCTITES 6 3 ENGINEERING PROPERTIES OF SOILS COMPRESSIBILITY amp SHEAR STRENGTH A INTRODUCTION 1 DETERMINE SUITABILITY FOR A USE A COMPACTED CONSTRUCTION OR FOUNDATION MATERIAL ROAD PERFORMANCE CHARACTERISTICS EXCAVATION CONDITIONS DRAINAGE 2 PREDICT PERFORMANCE HOW WILL IT RESPOND TO A USE B COMPRESSIBILITY DEGREE OF REDUCTION IN VOLUME A SOIL MASS MAY UNDERGO UNDER A NATURAL OR ARTIFICIAL LOAD DECREASE IN Vv MAINLY BUILDING ON THE SOIL 1 CONSOLIDATION COMPRESSIBILITY FROM A STATIC LOAD MAINLY BY DRIVING WATER FROM VOIDS A SETTLEMENT NATURAL CONSOLIDATION B COMPUTE H 1 TOTAL CONSOLIDATION EXPECTED VERTICAL DISPLACEMIENT A SOIL NATURE MORE IMPORTANT THAN LOAD AMOUNT B COMPARE VOID RATIO e TO P THE LOAD 102 EQUATION amp 103 LAB EXAMPLE 2 TIME REQUIRED FOR CONSOLIDATION A DEPENDS ON NATURE OF SOIL NOT LOAD INSTANTANEOUS FOR COARSEGRAINED SOILS SLOWER THE FINER THE GRAINED SOIL B LOW PERMEAB gt HIGH PERMEAB C THICK SOIL gt THIN SOIL D LOAD FIRST SUPPORTED BY PORE WATER LATER SOLIDS SUPPORT IT E STEP 1 DETERMINE Cv COEFFICIENT OF CONSOLIDAT USE COMPRESSION INDEX PERMEABILITY UNIT WEIGHT F STEP 2 USUALLY GO FOR 90 OF SETTLEMENT C TO REDUCE SETTLEMENT 1 REMOVE SOIL IF THIN 2 PLACE SURCHARGE ADDITION ON LOTS OF TIME BEFORE 3 ADD VERTICAL DRAINS FOR SPEED 2 COMACTION REDUCTION OF VOID SPACES BY MECHANICAL MEANS REPEATED LOADING amp VIBRATION ARTIFICIAL DENSIFICATION OF SOIL39WHEN SOIL USED AS CONSTRUCTION METERIAL BUILDING WITH THE SOIL A HOW SOIL PARTICLES REORIENTED TO FEWERVOIDS SOMTIMES GRAIN FRACTURES B WHY STRENGTH UP amp PERMEAB DOWN C TECHIQUES PUT SOILS IN LIFTS 18quot 1 ROLL ovERMANI TIMES 2 VIBRATION D CONTROL NEEDED 1 SELECT MATERIAL WITH RIGHT RARTICLE SIZE 2 WATER CONTENT THE MORE WATER CONTENT IN SoIL INCREASES RESISTANCE To REORIENTATION OF RARTICLES BI FORCE OF SUREACE TENSION ON WATER 2 OWC 0PTIMUM39WATER CONTENT PROCTOR TEST P 103 TOP OF CURVE WATER WHEN Mx DR DENSITY 4 FIELD MOISTURE To SEE IF AT oWC A SAMTLE TO LAD amp MOISTURE B NEUTRON PROBE NONDESTRUC C SHEAR STRENGTH RESISTANCE OF SoIL TO SLIDING OF ONE MASS AGAINST ANOTHER 1 How ToMEAsURE A DIRECTLY DIRECT SHEAR TEST B INDIRECTLY UNIAXIAL TRIAXIAL 2 MDHRCOULOM EQUATION AT FAILURE A SHEAR STRESS AT EAILURE B COHESION C ANGLE OF INTERNAL FRICTION 3 SHEAR STRENGTH IN NONCOHESIVE SOILS A C 0 NO COHESION B MU PORE PRESSURE C D FACTORS 1 DRAINAGE AS U UP SHEAR STRESS DOWN 2 VOID RATIO AFTER COMPACTION 3 DENSITY CONTROLS PHI 4 MEASURE BY DIRECT SHEAR 4 SHEAR STRENGTH OF COHESIVE SOILS A FACTORS 1 PI 1SHEAR STRENGTH 2 PARTICLE SIZE A SILTS LOW PI LOW TAU B CLAIS HIGH PI HIGH quot 3 MOISTURE CONTENT AS MOISTURE UP C DOWN DON39T LOSE WATER SO KEEP IN ZIP LOCK BAG 4 DECREASE IN VOID RATIO SHEAR STRENGTH UP ORE DENSE B OVERCONSOLIDATION EFFECTIVE STRESSES GREATER IN THE PAST CONSTRUCTION EROSION OF OVERBURDEN GLACIAL COMPACTION HUMANS C SENSITIVE CLAIS THIXOTROPIC CLAYS 1 LOSE STRENGTH WHEN GO FROM UNDISTURBED TO REMOLDED 2 IF gt 20 THEN SENSITIVE 3 MARINE CLAYS MAINLY SALTS REMOVED BY wEATHERINGAND LIQUIFY IMMEDIATELY 4 EQUATION 5 MEASURING SHEAR STRENGTH A DIRECT SHEAR ONLY FORNON COHESIvE SOILS NO PROVISIONS FOR UNDRAINED STATE B UNIAXIAL SIMA 1 C TRIAXIAL THREE SIGMAS CAN CONTROL COMERESSIVE AND CONFINING STRESSES 1 FOR BOTH COHESIVE AND NON COHESIvE SOILS 2 NEED UNDISTURBED SAMPLES 4 CLASSIFICATION OF ENGINEERING SOILS A BACKGROUND 1 PARTICLE SIZE AND PLASTICITY 2 PREDICT COMPACTION SETTLEMENT DRAINAGE FROST SUSCEPTIBILITY EXCAVATION PROBLEMS EMANKMENT CHARACTERISTICS 3 AS GRAIN SIZE DOWN PROBLEMS UP A CLAY MEIN PROBLEM DO EASIEST BY PI B UNIFIED SOIL CLASSIFICATION SYSTEM 1 CORPS OF ENGINEERSBUREAU RECLAM 1953 BASED ON CASAGRANDE 1948 P 956 2 USE 4 AND 200 SIEVES amp ATTERBERG LIMITS A IF gt 50 ON 4 GRAVELS B IF gt 50 PASSES 200 SILTCLAY SOIL c IF NEITHER OF ABOVE SANDY SOIL 3 USE LETTERS c AASHTO HIGHNAX PEOPLE 1928 US BUREAU RDADS AM ASS STATE HIGHNAX TRANS OFFIC 1 10 AND 200 SIEVES 2A1 A3 GRAVELS AND SANDS GOOD SUBGRADES 3 A4A5 SILTY EAIR SUBGRADE 4 A5 A7 CLAXEY POOR SUBGRADE D USDA SOIL SCIENCEGEOLOGY TEXTURES 1 USE 10 AND 230 SIEVES Engineering Geologya Laboratory Manual 62 I UNIFIED SOIL CLASSIFICATION SYSTEM I LABORATORY CLASSIFICATION CRITERIA Coarse Grained Soils GROUP Less than 50 passing No 200 sieve SYMBOLS Less than Cc between 1 and 3 Cu greater than 4 GW 5 passing GRAVELS Sig 32 Not meeting both C and Cu values above GP Less than 12 of coarse Atterbefg lim frac gn belowquotAquot line GM passes No 4 More than Above quotAquot line with Pl or Pl lt4 sieve size 12 passing between 4 and 7 requires No 200 use of dual symbols sieve size lGCGM A erberg I39m above quotAquotline GC or Pl gt7 Less than C greater than 6 Cu between 1 and 3 SW 5 passing MSANETS N 39 290 Not meeting both C and C values above SP ore an sieve size 1I2 of coarse fraction Atterberg hm passes NO 4 More than Above quotAquot line with Pl below quotAquotline SM sieve Size 12 passing between 4 and 7 requires use and PI lt4 No 200 of dual symbols sieve si2e SCSM quotquot 39be399 quotquot above quotAquothne SC and PI gt7 Borderline cases between 5 andT2 require use of dual symbols such as SWSC Fine Grained Soils GROUP More than 50 passing No 200 sieve SYMBOLS ML See adjoining plasticity chart CI lquotAquot line MH SILTS 39 1 AND CH CLAYS p Below quotAquot line and LL oven dry soil I LL air dry soil lt 075 OL I OH Visual identification Pt ET Figure 112Adapted from NAVFAC 1982 The Atterberg limits provide the means for de ning soil consistency for a cohesive soil They are based on the work of the Swedish soil scientist A Atterberg The Atterberg limits establish the relationship between thewater content and the physical state of the soil Figure 113 illustrates Atterberg limits and water content The solid and semisolid or nonpiasric state SL AER 1 I u ru 39139 Q9 Iquotl f Laboratory Classification Comparing soils at equal liquid limit 50 toughness and dry strength increase with increasing plasticity index Criteria 6 15 D E as C 60 greater than 4 u cl 539 D10 3 Z 393 D l2 395 1 3 an Cc g between 1 and 3 f 5 3 D10 X 1360 Fa 53 E 395 2 E E g Q g Not meeting all gradation requirements for GW 0 C 5 quot E quot3 U3 3 3 Atterberg limits below Aline or Above Aline with 392 E 333 E PI less than 4 PI between 3 395 5 U3 U3 9 g 4 and 7 are borderline C E 3 T3 Q Dug 5 Atterberg hrmts above Aline cases requiring use of J 9 m E g gg ga Dm 1 55 5 C D greater than 6 D H E 10 E 3 3 4 3 D l2 33 rra sw c i beuween1and3 3933 3939 D1ogtltD6o quot39 5 5 II on 239 3 1 5 393 Not meeting all gradation requirements for SW G G 5 I G J o o 5 E in g 3 395 52 Atterberg limits below Aline or Lmuta plotting In hatched 3 Y X 9 J E D PI less than 4 20112 W lLl39I Pl between 39 39393939 E 5 C 4 and 7 are borderline 3 3 33 Atterberg limits above Aline cases requiring use of E Q Q with P1 greater than 7 dual symbols cs quot5 5 Plasticity Chart h E For Laboratory Classification of FineGrained Soils er u g E 50 r r 1 t I I I T r H gt Iu U Q N quot5 Lu an OJ U D K 40 In D 5 E 30 2399 3 CL E 20 MH CLML 0 lt 1 E 77 3 0 I I I I I I i I O 10 20 30 40 50 60 70 80 90 100 Liquid Limit quotJ quotquot11i39rs 3 1 i39z39 D3o grain diameter in mm corresponding to 60 passing by weight as taken from grainsize distribution curve 39 rAi quot N IClEu B5equota ui D 5 UNIFIED SOIL CLASSIFICATION SYSTEM Group Field Identification Procedures Major Divisions Symbols Typical Names Iexcluding particles larger than 75 mm and basing fractions on estimated weights 1 2 3 4 5 H Gw Wellgraded gravelsgravel sand m tx wide quotquot183 in 879511 31393 find S115 IOI3IilltI39 l E 1 g C 3 te5 in or no fme5 amounts of all mteimediate particle sizes 55 533 3 53 g 3 E 5 2 GP Poorly graded gravels grsvel sand mix Predominantly one size or a range of sizes 6 3 3 lt3 6 tures little or no fines with 303119 mtennedmte 31333 U115 im 2 S 1 9 3 c N1 c 23 gt quot39 i 2 E 39 I 5 Nonplastic fines or fines with low la t39 t n 3 U 3 E P 3 5 mi E E GM Sill Jr Eravels gravelsandsilt mixtures for identi cation procedures 5eePMi1w ii 5 g Equot 3 g E 39quot quot39 E gt 3 quotquot 3 q 395 GO Clayey gravels gravelsandclay Plastic fines for identification procedures 393 n 391 E 9 39 CL be 1 5 U m n O mixtures 589 0W E E quot5 5 v 5 5 393 22 3 SW Wellgraded sands gravelly sands wide 75383 in 3133 and 5 1b5i39 I vlB1 E as 35 E E 5 5 3 lime or m nes amounts of all intermediate particle sizes O H 5 O E 41 3 quoti quot 2 5 L 0 vi quot D H 393 Q 41 39 39 g 3393 39f 2 E quot3 3 3 g Poorly graded sands gravelly sands Predominantly one size or a range of sizes 2 P n 3 quotE 5 5 39 SP ljme or no ne5 with some intermediate sizes missing F U I 393 quotquot 2 E E 5 E 2 is E 3 E quot39 quot quot3 M 3 5 c 3 Nonplastic fines or fines with low plasticity E 5 3 7 E 3 n 3 3 SM silty sands sandqm matures for identification procedures see ML below E D u D 39quot 939 u 1 3 an o i In in o 3 E Z 3 L E E Plastic fines for identification procedures quot39 3953 39 Cl d 39 E m 5 SC ayey san a sand clay mixtures See CL belowquot g F IderSiti tilaticE PrcIcedt6e S 3 on raction ma er in o ieve ize ca Dry strength Dilatancy Toughness 3 1 crushing reaction consistency Z9 characteristics to shaking near PL 39quot1 43 5 E E 5 Inorganic silts and very fine sands rock 3 2 3 ML flour silty or clayey fine sands or None to slight Quick to slow None 3 1 E39 clayey silts with slight plasticity In an 2 g C3 1 5 E Inorganic clays of low to medium None to van 395 393 CL plasticity gravelly clays sandy Medium to high Medium quot n cla 3911 1 1 cl U 2 ys 51 y c ays ean ays 3 E i 3395 539 Organic silts and organic silty clays of Slight to 0 393 01 low plasticity medium Slow Slight 5 5 E O m 3 MH 31 3quot i 39397i 7 quot quot l 339 35 Slight to Slow to none Slight to E 2 H 53 silty soils elastic silts medium medium E E I 391 fhihlati39t ft 1Iih 3939 U norganic c ays o g p s ci y a g to very E E E E E CH clays high None High E f 3 in E0 OH Organic clays of medium to high Medium to high None to very Slight to plasticity organic silts slow medium Readily identified by color odor spongy feel 393 393 quot15 Pt Peat and her hlghjy mgamc soda and frequently by fibrous texture After US Army Engineer Waterways Experiment Station 1960 quotThe Unified Soil Classi cation Systemquot Technical Memorandum No 3357 Appendix A Characteristics of Soil Groups Pertaining to Embankments and Foundations 1953 and Appendix B Characteristics of Soil Groups Pertaining to Roads and Air elds 1957 and A E Howard 1977 quotLaboratory Classi cation of Soils Unified Soil Classification Systemquot Earth Sciences T1nz m39ng Manual No 4 US Bureau of Reclamation Denver 56 pp Boundary classifications soils possessing characteristics of two groups are designated by combinations of group symbols For example GWGC well graded gravel sand mixture with clay binder bAll sieve sizes on this chart are US Standard G470570 SOILSIII 5 GEOLOGIC SOIL WEATHERED UPPERMOST LAYER OF ORGANIC AND INORGANIC ROCK FRAGMENTS CAPABLE OF SUPPORTING LIFE A ONLY JOB WHERE YOU CAN START AT THE TOP DIGGINGA HOLE A PROFILE SUCCESSION OF DISTINCTIVE LAYERS IN THE SOIL 1 O 2 A 2 E 3 HORIZON UNDECOMPOSED ORGANICS TWIGS NEEDLES LEAVES HORIZON TOPSOIL BLACK HUMUS DECOMPOSED ORGANICS AND MINERAL MATRIX ZONE OF BIOLOGICAL ACTIVITY HORIZON LEACHED ZONE WHITE COLOR IRON ALUMINUM ORGANICS REMOVED BY ACID WATERS INTENSE WEATHERING MAINLY IN FORESTS HORIZON ZONE OFACCUMULATION OF WEATHERING PRODUCTS IRON ALUMINUM CLAY REDDEST PART OF SOIL A Bt CLAY ACCUMULATION VERY STICKY FILMS B Bk CALICHE CALCITEF WHITE C Bg MOTTLED RED AND GRAY PATCHES POORLY DRAINED D Bx DENSE SILT FRAGIPAN HOLDS UP WATER E Bs VERY RED ABUNDANT IRON F Bw ONLY INCREASE IN SLIGHT RED COLOR 5 C HORIZON OXIDIZED PARENT MATERIAL 6 PARENT MATERIAL A ROCK B SURFICIAL DEPOSIT STREAM DEPOSIT DUNE GLACIAL MATERIAL LANDSLIDE C SOIL DEVELOPMENT SOIL GROWS AND CHANGES CHARACTERISTICS WITH TIME 1 DRY GRASSLAND 2 MOIST GRASSLAND 3 MOIST FOREST 4 WETLAND D FACTORS OF SOIL DEVELOPMENT BOOK 6 1 CLIMATEVEGETATION MOST IMPORTANT CLIMATE CONTROLS VEGETATION ANIMALS ANTS WORMS AND GOPHERS 2 TIME STRESSED ABOVE 3 TOPOGRAPHY SLOPE ORIENTATION AND ANGLE A SOUTH SLOPES WARMER AND DRIER B UPLANDS WELL DRAINED AND DEEP MEDSLOPES HAVE THIN SOILS LOWER SLOPES MANY TIMES ARE POORLY DRAINED amp HAVE BURIED SOILS 4 PARENT MATERIAL A GRANITE SANDY AND THICK SOIL B BASALT THIN CLAYEY SOIL E USES 1 ESTIMATING AGES OF DEPOSITS 2 FREQUENCY OF GEOLOGICAL HAZARDS A BURIED SOILS DATED PALEOSOLS B WHAT AND WHEN 3 EAST CLIMATES AND VEGETATIONS 4 PRODUCTIVITY OF CROPS 5 LAND USE PLANNING 6 SOIL EROSION WHICH SOILS WORST 7 WHERE ARE SHRINK SWELL SOILS G SOIL EROSION MAJOR ENVIRONMENTAL PROBLEM 1 RATES HIGH NONRENEWABLE RESOURCE A FORMATION 80 400 YEARS1quot TOPSOIL B EROSION gt NEW SOIL FORMATION BY 2 BILLION TONSYR IN US C EROSION OF 5 TONS OF SOIL FOR EACH TON OF GRAIN PRODUCED D FILLING IN RESERVOIRS RIVERS DELTAS 2 CAUSES AND CURESquot MAN HAS ACCELERATED A FARMERS ONTO MDRE STEEP LANDS amp SEMI ARID REGIONS TERRACE SLOPES B FARMERS MORE ROW CROPS ALTERNATE GRASS STRIPS WITH ROW CROPS ROTATION C MORE FARMLAND FROM FORESTS CONVERT LESS H SOIL SURVEYS 1 GENERAL ECOLOGYGEOLOGYCLIMATE OF AREA 2 SOILS PROFILE DESCRIPTIONS OF TYPE LOCALITIES 3 LAND USE BASED ON SOIL SERIES A ALSO SOIL CLASSIFICATION OF EACH B ENGINEERING CHARACTERISTICS OF EACH SOIL 4 GENERAL SOIL MAP OF THE COUNTRY 5 MAPS OF WHOLE COUNTYAIR PHOTOS I UNIVERSAL SOIL LOSS EQUATION A R K L S C P 1A ANNUAL SOIL LOSS TONSACREYR OR TONNESKM2YR 2 R RAINEALL EACTOR INTENSITY amp DURATION A 0350 HERE 100 350 FOR THUNDERSTORMS 3 K SOIL ERODIBILITY EACTOR A 0 TONSACRE HIGHEST FOR SILTSAND Low FOR CLAY AND GRAVEL INVERSELY PROPORTIONAL TO OM amp PROP TO PERMEA B T VALUE FOR39WHOLE PROFILE 5 IS HIGH AND 3 IS MODERATE AND 1 IS LOW 4 L FEET SLOPE LENGTH INCREASE L INCREASE EROSION 5 S SLOPE ANGLE INCREASE ANGLE INCREASEA 6 C CROPPING FACTOR HIGH FOR ROW CROPS 79 AND LOW FOR GRASSES AND WOODLANDS 16 7 P CONSERVATION TECHNIQUES CONTOUR PLOWING TERRACING ANYTHING THAT INTERRUPTS OVERLAND FLOW 0 10 8 TO REDUCE FOR CONSTRUCTION A CONSTRUCT DURING LOWEST RAINFALL PERIODS B CLEAR AREAS ONLY AS YOU NEED THEM C TEMPORARY VEGETATION ON SOIL STOCKPILES D DIVERSIONS PLASTIC FENCES DETENTION RASINS STRAW AND HAY BALES 6 PROBLEM SOILS A GLACIAL SOILS VARIABLE PARTICLE SIZE KAMES AND KETTLES IN THE TILL BIG BOULDERS B LOESS WINDBLOWN SILT 1 OPEN STRUCTURE SATURATE BEFORE BUILDING To DENSIFY IT BEFORE LOAD 2 WEAKLY CEMENTED HIGHLI ERODIBLE CUT CLIFFS VERTICAL AND GUTTERS AT BOTTOM C ORGANIC SOILS BOGS MARSHES SWAMFS PEAT 1 LOW STRENGTH HIGHLI COMTRESSIBLE 2 LOTS OF WATER IN THEM DRAIN 3 GOOD SOURCES OF TOPSOIL D EXPANSIVE SOILS CONTAIN SMECTITE 1 FORMED IN DRI39AREAS OR WITH VOLCANICS 2 EXPANDS WHEN39WET AND CONTRACTS WHEN DRY 50 2ooo VOLUME INCREASE 3 5 BILLIONYR IN US FOUNDATIONS ROADS 4 DETECTION EMS MODEL A PI gt 15 LL gt 36 CLAI gt 32 B HIGH RISK PI gt 29 LL gt 54 5 SOLUTIONS A DON39T BUILD ON IT B LOWACTIVITY SOIL BLANKET ON TOP USUALLI NEED AT LEAST 2 3 METERS C REINFORCED PIERS BELOW CLAIS So FOUNDATION IS FLOATING D LIME STABILIZATION CaOH2 E PORTLAND CEMENT STABILIZATION F FLY ASH STABILIZATION G ISOLATE WATER DRAINS PIPES MEMBRANES H GUTTERS ON HOUSES I HEAT STABILIZATION J TREES NO CLOSER THAN 12 EXPECTED HEIGHT IT IS APUMP K BUILD ON WELLDRAINED SITES L DON39T OVERWATER REPAIR LEAK PIPES 6 SOIL CLASSIFICATION CH OR VERTISOL E COLLAPSING SOILS DECREASE IN VOLUME WHEN SATURATEDF 1 DR SOILS AT EDGES OF MOUNTAINS ESP ON ALLUVIAL FANS 2 COHESION FROM GYPSUM AND CLAY IN VOIDS 3 COLLAPSE IRRIGATION DISSOLVES CLAX AND GYPSUMAND VOIDS COLLAPSE 4 HYDROCOMACTION 5 UTAH LAS VEGAS F QUICK CLAI SOILS SENSITIVE CLAXS 1 LOW39DENSITY SANDSSILTS MARINE 2 SALTS WEATHERED AWAX amp VIBRATION CAUSES DEPOSIT TO DENSIFY SO INCREASE PORE WATER PRESSURE AND DECREASE IN SHEAR STRENGTH TO ZERO amp DEPOSIT FLOWS G WETLANDS WET SOILS IF quotJURISDICTIONALquot THEN CAN39T BUILD UPON UNLESS YOU MAKE NEW ONE 1 HYDRIC SOILS MDTTLES39WITHIN TOP 20quot 2 HYDROLOGY PONDS39WATERAT LEAST 2 WEEKS EACH YEAR IN GROWING SEASON MARCH TO OCTOBER 3 HYDRIC PLANTS CATTAILS SEDGES WILLOWS TABLE 1 SLOPE STABILITY RISK CATEGORIES FOR EMBANKMENT SOILS GEOTECHNICAL HIGH INTERMEDIATE LOW TEST RISK RISK RISK LIQUID LIMIT gt 54 36 54 lt 36 PLASTICITY LIMIT gt 29 16 29 lt 16 CLAY CONTENT gt 47 32 47 lt 32 HIGH RISK CATEGORY INTERMEDIATE RISK LOW RISK CATEGORY 8590 chance of failure in 815 years after construction 5560 chance of failure in 815 years after construction lt 5 chance of failure in 815 years after construction I 39 39 39 39 a 39 39 A 7 39 539 39 39 I 39 39 nu r v A A J A 39 If LhL 39 c P n n L V 39 39 2 quot 4 39 P p quot I T quotA39 A39 quotquotquotquotquotquot39 39 r t I l 1 Ar 4 u u 39H 14 A n 39 a quot 1 THE FAFI SlDEf39 A 3 3 39 5 I I 39 u 39 quot39 E I quot quotquot 39 39 I quot x r quot quotELquot 1 1 39 I 39 5 397 39 39 2 I 39 A 39 4 39 kd Y 5 39 39 t I V d gt I 39 l 539 quot 39 a 39 39 k Bo A me 155 39 A 39 I l h V 3939 F P f 339 39 39 A hl Pl are a canch39 p p j p p n u I I I o 4 rn P 39 fquot quot 39 o o 39 I j39ff39 up a393939 quot quotquotquotquotquotquotquot F V 39 9 r L E 5 391 39 4 I O I E v 3 4 E i I t 1 F I zh o H i I V I r n 39 A quotquotuIn In 391 39 0 b quot 39 39 1 39 If 4 I quotu39i quot I quot mt quot 39 39 39 39 39 39 39 139 v X b 7n 7n e k God makes the snake A p e quot quot r quot 39 5 o 39 I U 39 39 A 39 39 I 39 3 C I 39 39 au A 39 39 A 39 39 I C 39 It 39 39 4 A an P j A quot 391 g 39 u I I 4 I A F I I 39 39 4 39 39 39 V A o Al A 39 7 39 u 39 39 K 39 I o 39 I I A A 39 39 A A v 39 I 39 n 39 I 39 v 39 A 39 I 39 I 39 I 4teL a sand 53 amp r39e ee 0 percent sand 2 395 FIGURE 38 Chart showing the percentages of clay be1ow 0002 nm silt 0002 to 005 mm and sand 005 to 20 mm m the basm sml textural classes Loam s 1 I 1 Clay H I 8 Silt loam I E I U3 I Silty clay loam i I I 39 Silt cuayl i 33 I 1 1 L I Loamy sand I l I and sand g 39 Sandy loam I g 3 E Sandy clay loam I 6 r 39 1 I E Sandy clay 1 E I 1 I None V Slight S ik339t fmd Very p as 10 STICKINESS AND PLASTICITY RATING Fig A1 Approximate relations between texture class grittiness and wet consistence 4u t 39 an w u 0 1 51 S01LDFSClllI TlOH SAMPLES PH I STANDAm7jEF39J5TNCmmON LEGEND 3 unr39AcJ3 ELEV n r3 1823 7 FE SPT 330 0 8 5 839 39 o 39 2 39 H quot339F 1quotquotquot quot Interlayered silty gravelly SAND and silty amauor nccovcnco sandy GRAVEL and gravelly SILT U mmwm3w I P1CllLiH5AMl39LE 7 IMPEHVGOUJ SEAL 1 lg 10 WATCH Lcv1 r391I20ucrr39n 1n ATTCHDEIIO ULHT3 B K Con1tHr 2 p PLASTIC LIIHT id NOTES 1 sou DESCRIPTIONS mo nmenmces me mnsnpne rave mo ACTUAL CHANGES war boulder at 1545 feet 35100 SE GHADUAL z warm LEVEL IS For one snowu mo MAY vIm WITH TIME OF YEAR V 9 light gray silty SAND 4 Q 13 volcanic ash at 20 feet 5 E 100 28 Brown clayey silty sandy GRAVEL interlayered with gravelly sandy silty a cm and clayey sm at 35 feet 34 7 3 19 1 35 d 6219C 4 40 xi Q 8 5 100 boulder at 42 feet Brown silty sand GRAVEL H basalt gravel Hole caving at 42 feet A F quotquotquotquot quotquotquotquotquotquot quotquotjquot quot J 9 20 Q l7 1 so p Bottom of hole W o 8 ge IIIfiiZZfZiI iffllifi wmncoremsencer TO I Job Dale Dic ll 3 R Drilling PEITON PARK T0071990 5 0310 III Lnndaudo T JOb N0 4 Slafl Finish Technology Drilling Technique Oder l1oLr1rz aocLTriCone E mnwquotW M nuc u um SUMMAQY BOQING LOG FIG 8 P3 39 1 Table 4C1 Summary of factors a ecting friction angle redrawn with permission of Prentice Hall from p 517 of An introduction to geotechnical engineering by RD Holtz and WD Kovacs Copyright 1981 PrenticeHall rW j u 4 Factor 39 Effect of Increase in Factor on b Void ratio e decrease Ahgularity A increase Grain size distribution increase Surface roughness R increase Water W decrease slightly Particle size S no effect with constant e Intermediate principle stress bps gt bu Overconsolidation or prestress little effect The frictional strength of gravelly material is in uenced by percentages of sand and gravel and by the relative density According to Hammond et al 1992 p 67 mj u n IInn Table 4C3 Consistency versus standard penetration test blow counts N relative density and friction angle for noncohesive soils after Peck et al 1974 Relative qa N Density for Sands Consistency Field Identi cation BPF D Degrees Very Loose below 4 below 15 25 to 30 Easily excavated with Loose hand shovel 4 to 10 15 to 35 27 to 32 Difficult to excavate Medium with hand shovel 10 to 30 35 to 65 30 to 35 Must be loosened with pick to excavate with Dense hand shovel 30 to 50 65 to 85 35 to 40 BPF is blows per foot see section 4C423 391 Residual Friction Angle O IlllTTW 7 I39f1T T TT39rlllT ITII IIII T171 0 10 20 30 40 50 60 70 80 Plasticity Index PI Figure 4C1I Reiationship of PI to residuai strength friction angle qb developed with permission of the American Society of Civii Engineers from data from quotSoii strengths from Back analysis of slope failures by JM Duncan and TD Stark In RB Seed and R W Bouianger eds Stability and performance of slopes and embankmentII Copyright 1992 American Society of Civii Engineers Geotechnical Engineering Division Yd PC e150 XV 140 e W E e r13920 Z Lm d Z 100 g P f L7g lt39IquotITYTItiTf1397iT1 IY amp in 3925 rm 15 an M 1 E Table 4C6 Stana39ard penetration test blow count N values and cohesion versus consistency for cohesive soils after Peck et ai 1974 N Cohesion Consistency Field Identi cation BPF c psf Very Soft Easily penetrated several inches below 2 0 to 250 by fist T 39 quot Q Soft Easily penetrated several inches 2 to 250 to 500 quot by thumb O 2 Firm Can be penetrated several 39 39 39 39 4 to 8 500 to 1000 inches by thumb with moderate effort Stiff Readily indented by thumb but 8 to 15 1000 to 2000 penetrated only with great effort Very Stiff Readily indented by thumbnail 15 to 30 2000 to 4000 Hard Indented with dif culty by over 30 gt 4000 thumbnail BPF is blows per foot see Section 4C423 45 40 3 5 35 E Wi r 0 n E 30 1 L e 339 T 0 E 25 K E 20 3 F 53 i sg 15 1 1 J ifs 10 I g 5 0 2 1 10 100 Plasticity Index PI Figure 4 C 6 Relationship of P1 to peak strength friction angie from an equation in Hammond et al 1992 4C 389 S p kJ P 96 W G39 3939 539V A 4 1 av39quot quot kA gt4PrL 393 SP 4 quot V S 39Vw 5 Lsquot PLASTIC 50113 39 ZW C PL I SPLIT spoon mum of BLOW COU Tquot HAND TEST CONSISTENCY HATERIRL COHESIGN PEI INTERNAL FRICTION PLASTICITY PIu I i I i 4 2 p 391 t 1quot Jory soft E very sort c1aymud 51ts 5 250 2 h was to 3 ight 5 39 39 39 i I 2 I 2 lf1at H111 dent soft 39 silty u1ayaandy clay 250J5oo I 4050 5118 t 15 l8 stick thumb intu firm firm cay aamdy ailts dunno silty clays 500100O 53910 medi 1020 P Clnodzhun 39 I 1 815 thulub u111 dent stiff stiff clays 10002000 10 12 1113 2940 t p 15 thumbnail H111 very stiff very tlff clays I 3oool4 ooo 13391l very high 39 l0 indent th b all 111 h d I 0 30 um n no indent ar hard clays fat clay H000 1 20 very high 10 r n j 7 Typt39cai properties of compacted materials reprinted from Driscoll 1979 Typical value of k Range of Range 01 cormression Typical strength characteristics Typml Group Sci maximum optimum Cohesion 1 coefficient of Symbol Type dry unit rnolsture At At As Cohesion Effective 39 Tani permeability weight percent 20 psi 50 psi compacted saturated stress itmin pd P psi psi envelope ercent of original degrgas j1jj ow Well graded clean 125135 110 03 06 0 0 ea gt079 5 x 10 gravels gravelsand mixtures GP Poorly graded clean 115125 1411 04 09 0 0 gt37 gt074 101 gravels gravelsand mix GM Silty graveis poorly 120135 128 05 11 gt34 gt057 gt10 6 graded gravelsend silt GC Clayey gravels 115130 149 07 16 gt31 gt060 gt10 7 poorly graded gravelsandclay sw Well graded clean 110130 150 06 12 0 0 ea 079 gt10 3 sands gravelly sands SP Poorly graded clean 100120 2112 08 14 0 0 37 074 gt10 3 sands sandgravel mix SM Silty sands poorly 110125 1611 08 16 1050 420 34 067 5 X 105 graded sandsilt mix SMSC Sandsilt clay mix 110130 1511 08 14 1050 303 33 066 2 X106 with slightly plastic nes SC Clayey sands 105125 1911 11 22 1550 Z3 31 39 060 5 X 107 poorly graded sand clay mix M inorganic silts and 95120 2412 09 17 1400 190 052 gt10 5 clayey silts MLCL Mixture of inorganic 100120 2212 10 L2 1350 4amp1 32 062 5 X 107 silts and clay CL inorganic clays of 95120 2412 13 25 1800 270 054 gt10 397 low to medium plasticity OL Organic silts and 80100 3321 siltclays low plasticity MH inorganic clayey 7095 4024 20 36 1500 420 5 047 5 X 107 silts elastic silts CH inorganic clays of 75105 3619 26 39 2150 230 19 035 gt10 7 high plasticity 11 Organic clays and 65100 4521 slly clays Notes All properties are for condition of standard proctorquot maximum density except values of kwhich are tor quotmodified proctor maximum density Typical strength characteristics are tor etlective strength envelopes and are obtained from USER data Compression values are for vertical loading with complete lateral confinement gt indicates that typical property is greater than the value shown indicates insufficient data available for an estimate 392 4C Table 4C10 Summary of field methods for detennining shear strength adapted from Holtz and Kovacs 1 compressive strength 21 Figure Test Use Number Best For Remarks Limitations Vane shear test Lab eld 4Cl9 Soft to stiff Various sizes and con gurations May overestimate 1 see VST clays available for both eld and lab use gure 4C20 for correction Heightdiameter ratio HID 2 for factor for very soft clays eld vanes IID 1 for lab vanes Unreliable readings if vane Only lab vane sample is seen encounters sand layers varves stones etc or if vane rotates too rapidly Dutch cone Field 4C2l All soil types A 60 cone with a projected area of Boulders cause problems penetrometer test except very 10 cm is pushed at 1 to 2 mmin Requires local correlation CPT coarse Point resistance q and friction on for soft clays granular soils the friction sleeve f are measured either electrically or mechanically Standard Field 4C23 Granular soils A standard splitspoon sampler is Very rough correlation with penetration test driven by a 635 kg hammer falling 1 for cohesive soils SPT 076 m The number of blows Boulders can cause required to drive the sampler 03 m problems Results are is called the standard penetration sensitive to test details resistance or blow count N 39 Disturbed sample obtained Iowa borehole Field 4C25 Loessial Device is lowered into a borehole Cannot be used with soils shear test BS39T silty soils and expanded against the side walls with 10 or more gravel or 6 Then entire mechanism is caving sands Uncertain pulled from ground surface and drainage conditions during maximum load measured 1 shear make the test dif cult Stage test results are used to plot to interpret Is it CD or Mohr diagram for CD tests Range CU or somewhere in of s is from about 30 to 100 kPa between Pressuremeter Field 4C26 All soil types A cylindrical probe is inserted in a Requires a correlation PMT drill hole may be selfboring between p and 1 Lateral pressure is applied incrementally to side of hole Torvane TV Lab eld 4C27 Very soft to Hand held calibrated spring quick Cohesive soils without stiff clays used on tube samples or the sides pebbles ssures etc Test of exploratory trenches etc only a small amount of soil Sample tested is seen near the surface Only 39 rough calibration with 1 Pocket Lab eld 4C28 Very soft to Same as above except spring is Same as above penetrometer PP stiff clays calibrated in uncon ned 4C 39 411 G47053970 ROCK MECHANICS 1 ROCK MATERIALS A TYPES OF MATERIAL 1 ROCK DENSE AGGREGATE OF MINERALS 2 SOIL ROCK PARTICLES AND MINERAL SEDIMENTS EASILY EXTRACTED 3 FLUIDS WATER GAS MAGMA PETROLEUM B ENGINEERING CLASSIFICATION OF ROCKS 1 GEOLOGIC NAME OF ROCK BASED ON MINERALS 2 ROCK SUBSTANCE STRENGTH AND DEFORMATION PROPERTIES OF INTACT UNFRACTURED ROCK INTACT ROCK 3 ROCK MASS CONTINUITY CHARACTERISTICS BEDDING PLANES FRACTURES FAULTS JOINTS C ROCK SUBSTANCE CLASSIFICATION ASTM METHODS 1 SPECIFIC GRAVITY 2 POROSITY PERCENT HOLES 10 LOW 40 3 VOID RATIO VVVs 4 DURABILITY A HARDNESS ABRASION RESISTANCE TO SCRATCHING B TOUGHNESS RESISTANCE TO SUDDEN IMPACTS C SOUNDNESS RESISTANCE TO FREEZETHAN AND WET AND DRY CYCLES 5 UNCONFINED COMPRESSIVE STRENGTH LIMITING FORCEAREA A MATERIAL CAN WITHSTAND WITHOUT FAILUE FAILUE CRACK A SEE CHART STRENGTH PSI gt32000 16 32000 9 16000 4000 8000 lt4000 6 DEFORMRTION BEHAVIOR A B C D 7 SHEAR STRENGTH 8 TENSILE STRENGTH ABOUT 25 TO 60 OF COMPRESSIVE STRENGTH CGS Kgcm2 gt 2250 1125 2250 562 1125 281 562 lt 281 PLASTIC ELASTIC POISSONS RATIO DESCRIPTION VERY HIGH HIGH MODERATE EAIR POOR MODULUS OF ELASTICITY FIELD TEST PING THUD NO MARK THUD FRACTURE THUD IMPRINT BURY HAMMR V CHANGE DIAMETERCHANGE LENGTH UNITLESS MAX 5 INVERSELY PROP TO COMPRESSIVE STRENGTH amp ELASTIC MDDULUS 1 GRANITE 23 BASALT LIMESTONE 25 MARBLE GNEISS 21 SCHIST SHALE 08 TAU f c phi 23 12 2 ENGINEERING CHARACTERISTICS OF IGNEOUS ROCKS A INTRUSIVES 1 STRENGTH HIGH TO VERY HIGH 16000 32000 PSI 2 DEFORMETION AND FAILURE ELASTICPLASTIC B EXTRUSIVE MASSIVE FLOWS DIKES SILLS 1 STRENGTH HIGH 16000 32000 PSI 2 DEFORMATION AND FAILURE ELASTIC C EXTRUSIVE POROUS VESICLES TUFF BRECCIA PUMICE SCORIA 1 ROCK STRENGTH VERY LOW TO LOW 0 8000 PSI 2 DEFORMRTION AND FAILURE PLASTIC ELASTIC 3 ENGINEERING PROPERTIES OF SEDIMENTARY ROCKS A CLASTIC SEDIMENTARY ROCKS VARIABLE DEPENDING UPON SORTING MINERALS CEMENTATION VOIDS 1 STRENGTH VERY LOW SHALE TO VERY HIGH QUARTZ CEMENTED SANDSTONE 2 FACTORS A HIGH STRENGTH GRAINS UP B INCREASED SORTING POORLY GRADED DOWN C INCREASED ROUNDING DOWN D INCREASED CEMENTATION UP E INCREASED VOIDS DOWN 3 DEFORMATION USUALLY PLASTICELASTIC WITH VOIDS COLLAPSING AT FIRST 4 SHALE RED FLAG WEAK ROKI 1 LOWER SLOPE ANGLES SLOPE STABILITY PROBLEMS WEAK FOR FOUNDATIONS B LIMESTONE 1 STRENGTH 139EDIUM TO HIGH 16 32 kpsi 2 DEFORMATION PE IF MICRITE P EP IF FOSSILIFEROUS 3 STRENGTH DECREASES WITH INCREASED CLASTIC PARTICLES AND FOSSILS IN IT DECREASES WITH INCREASE IN VOIDS C EVAPORITES GYPSUM ROCK SALT amp COAL 1 STRENGTH VERY LOW TO LOW lt 8 kpsi 2 DEFORMATION ELASTICPLASTIC 3 FACTORS A DISSOLUTION CREATES WEAK ZONES 4 ENGINEERING PROPERTIES OF METAMORPHIC ROCKS A QUARTZITE AND HORNFELS 1 ROCK STRENGTH INCREASED FROM MTAMORPH A HIGH TO VERY HIGH 1632 KPSI 2 DEFORMATION amp FAILURE ELASTIC B SLATE AND PHYLLITE 1 ROCK STRENGTH MEDIUM TO HIGH 832 KPSI 2 DEFORMATION amp EAILURE ELASTIC C MARBLE 1 STRENGTH MEDIUM 8 16 KPSI 2 DEFURMATION amp FAILURE ELASTICPLASTIC D SCHIST DEPENDS ON FOLIATION amp LOADING 1 PERPENDICULAR TO FOLIATION A HIGH STRENGTH 1632 KPSI B ELASTIC DEFORMATION 2 PARALLEL TO FOLIATION A STRENGTH LOW 48 KPSI B DEFORMBTION ELASTIC 3 IN BETWEEN FOLIATION A STRENGTH INTERMEDIATE B DEFORMATION IN BETWEEN E GNEISS NO PLANES OF WEAKNESS 1 STRENGTH MEDIUM TO HIGH 8 32 KPSI 2 DEFORMATION ELASTICPLASTIC F PROBLEMS WITH METAMORPHIC ROCKS ZONES OF WEAKNESS WATER INFLOW OVERBREAK IN TUNNELS 1 ST FRANCIS DAM FAILURE 1928 LOS ANGELES A FAILED FEW MONTHS AFTER BUILT 400 DEAD WALL OF WATER 30 50 M HIGH B WATER INTO FOLIATION CRACKS amp YELLOW ZONE FAILED amp DAM FAILED ALSO PART OF ANCIENT LANDSLIDE C CROSS SECTION 2 HAROLD TUNNEL DENVER WATER BOARD TUNNEL 37 KM LONG CONCRETE LINED THROUGH IGNEOUSMETAMORPHICS A INFLOWS OF GROUNUWATERALONG CRACKS MORE GROUT MORE COSTS 1 GNEISS gt SCHIST gt GRANITE B MORE OVERBREAKS IN METAMORPHIC ROCKS MORE COSTS 1 GNEISS amp SCHIST gt GRANITE 2 DIAGRAM or TUNNEL PAYLINE OVERBREAK n 0 K A oNuJm H w C VHS J m 2 m m n H c A w B mw H T D H 1 n YN I ma o em m w O0 snnuvy m I U h mm M ms mu 0 GM M h 8 mm x mm m L we mn n D mm 1 6 om H GL 4 m n cm Em m ma 1 U m m wh pb E M W U E m M 2 L D E G m n n d V5 N a k u e x m C C S TLu w E w m m R e 1 T w M 1 nu 0 O 0 O O 0 6 3 nu O 0 6 4 2 1 O O 3 2 1 3 x was m mUoE mmogt 1 A Id L 4 3 G47053970 ROCK MECHANICS II WEATHERINGROCK MASS 5 ROCK MODULUS DEERE AND MILLER 1966 A HIGH MODULUS RATIO ELASTIC DEFORMATION 1 CONCRETE AND STEEL gt 5001 B MEDIUM MODULUS RATIO MOST IGNEOUS ROCKS HERE BEST PERFORMANCE HERE ALSO GNEISS RASALT LIMESTONE 2001 TO 5001 B LOW MODULUS RATIO NONELASTIC DEFORMATION 1 SHALE HERE lt 2001 2 SEE OVERHEAD 6 WEATHERING EFFECTS OF STRENGTH MAINLY CHEMICAL A CLASSIFICATION OF WEATHERING DEVELOPED MAINLY FOR CRYSTALIINE ROCKS LIMESTONE ALWAYS I QUARTZITE ALWAYS I OR II 1 FRESH IA NO VISIBLE SIGN OF WXING 2 FAINTLY WEATHERED IB DISCOLORATION ON MAJOR JOINT SURFACES 3 SLIGHTLY WEATHERED II DISCOLORATION ON AIL DISCONTINUITIES 4 MODERATELY WEATHERED III lt 50 DECOMPOSED quotWEAKENED ROCKquot 5 HIGHLY WEATHERED IV gt 50 DECOMPOSED 6 COMPLETELY WEATHERED V100 DECOMPOSED BUT ROCK STRUCTURE STILL THERE SAPROLITE 7 RESIDUAL SOIL VI CONVERTED TO SOIL 5 NO ROCK STRUCTURE LEFT B LOSS OF COMPRESSIVE STRENGTH WITH WEATHERING GRANITE EXAMPLE 1 IA FRESH gt 250 MPa 2 IBII DISCOLORED 100 250 MP3 3 III V WEAKENED 25 100 MPa 4 VI SOIL lt 25 MPa C WHY LESS STRENGTH INCREASE IN POROSITY D INDEX TESTS IN LAB AND IN FIELD 1 POINT LOAD TEST 2 SCHMIDT HAMMR TEST REBOUND INVENTED FOR CONCRETE BUT WORKS ON ROCK 3 SLAKEDURABILITY TEST DETERMINES quotWEATHERABILITYquot OF CLA RICK SoILS A FOR ROCKS lt 25 MTa B SINGLE AND DUBLE CYCLES LOOK AT LoSS OF MASS OF EXAMPLE 7 ROCK MASS CONTINUITI OF MASS A OVERALL STRENGTH OF ROCK RELIES MDRE oN ROCK MSS THAN INTACT ROCK NoTAS BIGA THING IN SoILS WHERE THE STRENGTHS ARE SO SMALL 1 BASED oN FIELD oBSERvATIoNSMAINLI B WHY DISCONTINUITIES BAD 1 REDUCE STRENGTH OF ROCK 2 PAIHWAIS FoRWATER 3 EAILURE SUREACES UPON UNLOADING 4 INFILLINGS CAN39WEAKEN ROCK CHLoRITE TALC GRAPHITE CLAY A INFILLINGS THAT STRENGTHEN ROCK QUARTZ AND CALCITE PRECIPITATES C TYPES AND EXTENT OF DISCONTINUITIES 1 JOINTS FROM COOLING AND PRESSURE RELEASE LIKE EXFOLIATION COLUMAR JOINTING A MANY CRACKS DETERMENE WEAK PLANES 2 BEDDING AND STRUCTURE IN SED ROCKS A MASSIVE gt 2M LAYERED lt 2M B LITHOLOGIC CONTACTS LIKE SS TO SH 3 FOLIATION 4 FAULTING FRACTURES WITH DISPLACEMENT A EXAMPLE EISENHOWER TUNNEL CO HIGHEST VEHICLE TUNNEL IN WORLD 27 KM LONG AT 3400 M ELEVATION TIME 5 YRS WITH 13 DOWNTIME COST 112 OF 495 MILLION ORIGINAL COST MAJOR PROBLEM SHATTERED ROCK IN FAULT ZONE HAD TO PUMP FULL OF GROUT BEFORE EXCAVATE D CHARACTERISTICS OF DISCONTINUITIES FIELD DESCRIBED 1 ORIENTATION IMPORTANT FOR SLOPE STABILITY A DO JOINTS INTERSECT DAYLIGHT SLOPE AT lt SLOPE ANGLE B ARE PLUNGE ANGLES lt ANGLE OF FRICTION C USE STEREONETS D EXAMLES DIP SLOPES WHEN JOINTS PARALLEL TO SURFACE VAIONT DAM ITALY MADISON CANYON MT FRANK BC E PRODUCES SLAB FAILURES 2 SPACING A CLOSE STRENGTH WAY DOWN B DISTANT STRENGTH FROM INTACT ROCK C INTERSECTING JOINTS ROCKFALL SOURCE AREAS WEDGE 3 CONTINUITY THEY EVENTUALLY CLOSE WHEN HOW LONG 4 SURFACE CHARACTERISTICS A WAVINESS INCREASES FRICTION B ROUGHNESS ASPERITIES PROJECTIONS SMALL SCALE WAYINESS THAT INCREASE FRICTION C DRAW PROFILES 5 SEPARATION AND FILLING LOWERS SHEAR STRENGTH DESCRIBE THICKNESS AND TYPES CLAY SILT GOUGE SAND 6 WEATHERING REDUCES STRENGTH USE I quotVI E CORE RECOVERY AMOUNT OF CONTINUITY FROM CORE 1 RANGE 0 100 2 CORE RECOVERY LENGTH OF CQRE RECOV LENGTH DRILLED QORE RUN F RQD ROCK QUALITY DESIGNATION DEERE 1968 1 SIMLE MOST USED WAY TO DESCRIBE ROCKS 2 MODIFICATION OF CORE RECOVERY ONLY USE PIECES OF CORE gt 10 CM 4quot amp ADD 3 CORE MUST BE gt 54 cm WIDE LESS WILL PRODUCE CRACKS IN DRILLING 4 CHART RQD 35 DESCRIP FRACTURE SPACING 0 25 VERY POOR lt 5cM VERY CLOSE 25 30 POOR 5 30 CM CLOSE 30 75 FAIR 30 CM 100 CM MOD WIDE 75 90 Goon 1 3 M WIDE 90 100 EXCELLE39N39I39 gt 3M VERY WIDE G NORMALIZED RQD JEFF KEATON AGRA 1982 1 PROBLEM RQD SUBJECTIVE DEPENDS ON CORE LENGTH DRILLER DIAMETER OF CORE 2 SOLUTION DETERMINE RQD ON RUNS NOT LENGTHS A NORMALIZED TO A PER FOOT BASIS ON EACH SECTION OF SIMILAR MATTER 3 EXAMPLE H USING RQD FOR TUNNELING METHODS 1 SOFT GROUND METHODS LOW RQD amp STRENGTH 2 DRILLING AND BLASTING MED RQD amp MOST STRENGTHS 3 TUNNEL MACHINES HIGH RQD amp ANY STRENGTH I USING RQD FOR EFFECT ON SEISMIC VELOCITIES 39 Rack Strength it Pq i L p r 39 E J at I 39 n n a o t u o I I o 39 oI393939o39 39 0n Iou39I39oo o39OoIuI a o39 0139o 0 39 39 o 39 39 I u c 39 I u 39 O o 39 39 I 39 o o 39 39 39 I a I 39 o 39 o 39 I u I o 39 I 39 0 o 39 I n 0 o I 39 I 39 I u 39 39 I 39 I u 0 U U g I I 39 39 I I I 39 o 39 39 I o u 39 39 39 o 39 I o 39 39 I u 39 39 u u 39 39 I 39 o 39 39 I A 39 39 I a 39 39 I n 39 39 I o 39 39 I a 39 39 I I u 0 u g 39 I u 39 I a u 39 o o I 39 I n o c n 39 I s 39 39 0 o 39 39 39 39 I 39 O I I I I 39 I o 39 u 0 I u 39 I o 39 I o 39 U u I o 39 0 u 39 O 39 O o 39 I n u 39 I I u lI0II39Iu39lo 39 39 39 39 39 39 I39u3939o390 39393939393939393939393939393939 39 39 I Q 1 A v loo Nmm l0 t3939 39393939 39 39 395fs55s35ss55 TU n F 8396 0e m ac h I n es 0 g 0 100 Rock Quality Designation RQD Figure 450 Diagram of tunneling methods most appropriate for given rock strengths and RQD conditions Reproduced by permission of the Geological Society of i London from A M Muir Wood Tunnels for Roads and Motorways Q J Eng Geol Vol 5 No I 1972 ii g g g s 9 39 39 5 39 39 Y 1 5 V 2 1 39 u n y 1 5 4 n mutt r 1 v V1 Ir vLquot39gtu Ipl Iris IugIIIw2 9 re 14 9 q r 39vno in IInv1l PI fquot39 1I A h139quot393ln A a39 Au w w r o I 1 1 n 0 o 5 39 I I 39 h39r n u J ROCKMhSS CLASSIFICATION IMPORTANT FOR UNDERGROUND OPENINGS ROCK CUTS OPEN PIT 1 2 3 4 5 6 MENES TUNNEL SUPPORT ROCK STRUCTURE RATING WICKHAM 1972 SPECIFIC FOR TUNNELS QSYSTEM MINLY FOR TUNNELS BARTON ET AL 1974 NORWAY GEOTECHNICAL INSTITUTE COMPLICATED TERZAGHI 1946 QUALITATIVE FRANKLIN ET AL 1971 A USES SPACING amp STRENGTH PRODUCES 6 CLASSES VL VERX LOW T0 EH EXTREMLY HIGH B SEE CHART p 199 BIENIAWSKI 1973 ROCKMASS CLASSIFICATION A COMPARES STRENGTH T0 SPACING B SEE CHART P 201 BIENIAWSKI 1974 GEOMECHANICS CLASSIF A COMPARES 1 INTACT ROCK STRENGTH 2 RQD 3 SPACING 4 ORIENTATION PARALLEL OR PERPEND T0 SLOPE RELATED TO TUNNEL AXIS SEE CHART P 203 5 JOINT CONDITIONS TIGHT VS OPEN 6 GROUNDWATER INFLOW PER 10 m0F TUNNEL B GET ROCKMSS RATING RMR SEE P 204 FOR EXAMPLE 7 WILLIAMSON 1988 UNIFIED ROCK CLASSIFIC A GIVE LETTER FOR EACH OF 4 EACTORS 1 DEGREE 0F39WEATHERING 2 STRENGTH 3 PLANARLINEAR FEATURES 4 UNIT WEIGHT B AAAA LEAST DESIGN EVALUATION EEEE MDST DESIGN EVALUATION Uniaxial compressive strength MNm2 125 5 ModeQtey 125 Moderately 50 100 Very 200 Extremely 5 Very weak Weak weok strong Strong strong strong 3a Very EH EH thick 2 Rock quality VH V Thick 9 E ore E p J 5 an H H Medium to E S 4 3 I g E 1quot Z391 quotquot U Q I A P quot 3 L 39 E 39 L I 39 391 M M Thin 39 o 0 0 0 0 0 0s 39 I 39 I39 Q quot 39 0 Very 2 L L i thlrl 0 002 4 0006 39 39 EL VL L M H VH EH 003 0391 0393 1 3 10 39V i 4 l I q E 5 Strength 15 MNm2 Figure 462 Rock mass quality classi cation based on UCS and discontinuity spacing where I point load index and classes range from very low VL to extremely high EH Reprinted with permission from Trans Inst Min Meta Vo80 Sec A Bull 770 J A Franklin E Broch and G Wa the Mechanical Character or39if5Ek 5 lton 1971 Logging Li K1 A l Jm n 44 Md iJ 4 w z z mam W R U Pko 1 L b uu 0 s K6 L 13 x w y m n m H E II 2 41 i MW 2 wn n IJ G d ry 0 1 u pP I run afl smw 0i V A M QT 0 A 1 r ruvai t F 1IrWI ii 1 lr 1 E41 n H I l m n C 8 c 0 0 Li I p p 1mm m p G 0 S n C 5 m m M D n rl M H m Aq m og W m H Hm I m m 0 W 1 U D Q N A e IH nM O R m rl Vin M W F m E u b 9 mm W I I4 m N n u r m 0 m 9 S W J n n 8 WM mm J W U x S S A I A OEdm S M Mu In 9 G M LQuOIr S D C I B W r A M s s 9 n W 1 M I m n N m r o K O m o M Rom a M c Z A e ADnu HM Ka ll mu m M M MM G2 A cm s 5 W n K NO Mmo m m V d 1 M Pun2unul4uOluh4nmuu mo J3 0 n In T 0 mm Tom c9 Tm w ow H S 410 my Dnl gt nnnw munm Enlt J O 3 ltmIGm M0 M0 W0 ln W Lsn Nam Umm Kmm am J no 99 TummrO9H nueh AH nwhuerd lg qun1 I IRnm Em Eom mm I B e E M ITnwF MCH WCF WCF h cw 3 Um 0 v e E EM M M 0 4cis mm m M 0 M 4 cm onwh M M M M M 4 m M raet O 0 O 5 S MrQ 0 O 5 2 m T g nn Capm 2 1 U H I I15 Mu aummrl w e I C mUO g n I C3 A I 4 0 K L F S A R b Z03 5439aamp5 Table 419 Geomechanics Classi cation Parameters Ranges Ratings and Classes a Classi cation Parameters and Their Ratings USC of intact rock gt200 MPa 100200 MPa 50100 MPa 2550 MPa lt25 MPa 1 Rating 10 5 2 1 0 r Drillcore quality RQD 90 to 100 75 to 90 50 to 75 25 to 50 ltv5eVt 39e399quotV 2 Rating 20 17 14 8 3 Spacing of joints gt3 m 13 m 03 m 50300 mm lt50 rnm 3 Rating 30 25 20 10 5 orirttlteio1rsdo395ints tav3Er23le Favorable Fair Unfavorable unto fnrr ble 4 Rating 15 13 I0 6 3 Condition of joints Very gtc1LU0 mm a2jhcoti1nrlt1s CFC frhtinufLTsm OF3CrtijOJ1 No gouge Gouge lt5 mm Gouge gt5 mm 5 Rating 15 10 5 0 Groundwater in ow None lt 25 25 125 gt125 per 10 m of tunnel length Imin lmin Imin 6 Rating 10 8 5 2 b RockMass Classes and Their Ratings Class No I ll Ill IV V PP t Description of class Very good rock Good rock Fair rock Poor rock Very poor rock Total rating l00lt 90 90lt 70 70lt 50 50lt 25 lt25 Source Modi ed from Bieniawski 1974 p1t1row o11rnp p1cIr1uIP Note 7 UNIFIED ROCKCLASSIFICATION For Design and Construction Evaluation D AI DEGREE OF WEAIHERING Hand lens Fresh State Visually Fresh State Stained State Partly Decomposed State Williamson Completely Decomposed State ABBREVIATION MFS VFS STS PDS CDS SPECIMEN STRENGTH Unconfined Compressive Strength Greater than 15000 psi gt1080 TSF 8000 to 15000 psi 5761080 TSP 3000 to 8000 psi 216576 TSF 1000 to 3000 psi 72216 TSP Less than 1000 psi lt72 TSF PLANARand LINEAR FEATURES SolidRandomBreakage SolidPreferredBreakage Latent Planes of Separation 2D Planes of Separation 3DP1anes of Separation UNIT WEIGHT Greater than 160 lbscuft 150 to 160 lbscuft 140 to 150 lbscuft 130 ta 140 lbscuft Lessthan130 lbscuft gt256 240 to 256 224 to 240 208 to 224 lt208 AAAA Requires least design evaluation EEEE Requires most design evaluation 0 in sequence means quotno determinationquot Some combinations do not occur for example Completely Decomposed State and Greater than RQ PQ DQ CQ MEL SPB LPS 2D 3D gt160 150160 140150 130140 ltl30 15000 psi Solid random breakage and Greater than 160 lbscuft EAAA CONSTRUCTION MATERIALS 1 INTRODUCTION 30 OF MATERIAL MINED EACH YEAR ARE FOR CONSTRUCTION A FOUR CATEGORIES OF MATERIALS EXTRACTED FOR USE BY HUMANS 1 METALS AND METALLIC ORES 2 MINERAL IUELS 3 GROUND WATER 4 INDUSTRIAL ROCKS AND MINERALS 2 ECONOMICS OF NATLIRAL MATERIAL FOR BUILDING A UNIT VALUE VALUE PER TON B PLACE VALUE VALUE BASED ON DISTANCE FROM THE SOURCE TO MARKET 1 AUSTRALIA GRAVEL HAS HIGH PLACE AND UNIT VALUE SINCE VERY LlT39l39LE THERE 2 CONSTRUCTION MATERIALS RARELY IMPORTED OR ExPORTED BECAUSE Low UNIT VALUE 3 DIMENSION STONE BUILDING STONE MECHANICALLY CUT A USES 1 EXTERIORIINTERIOR IINISH 2 FLOORING 3 MONUMENTS 4 SIDEWALKS B SOURCES MAINLY QUARRIES C HISTORY OF DIMENSION STONE IN US 1 PRE1945 COMMON IN ALL BUILDINGS A WASHINGTON MONUMENT MARBLE FROM 3 QUARRIES 1845 1885 2 POST 1945 COSTS TOO HIGH SO USED LESS A ONLY FOR ENTRANCES 8 LOBBIES B ARTIFICIAL COMBINATION OF RAW D PRODUCTION IN US 1986 STONE TONNAGE 1 GRANITE 74 2 LIMESTONE 62 3 MARBLE 3 4 SANDSTONE 34 5 SLATE 16 6 OTHERS 6 E DESIRED cHARAcTERISTIcS 1 EASE OF QUARRYING 2 DURABllTY AND SLOw WEATHERING 3 COLOR BEAUTY 4 FREE OF IRON 5 TAKES POLISH MATERIALS VALUE MIL 42 36 26 22 18 F EXAMPLES 1 MOST USED GRANITE BECAUSE WEATHERS SLOWING AND STRONG AND BEAUTIFUL 2 MARBLE TODAY USED MAINLY INSIDE BECAUSE OF ACID RAIN WEATHERING ON BUILDING EXTERIORS 3 SANDSTONE BEST ONES WITH QUARTZ CEMENT 4 SLATE EXPENSIVE TO QUARRY BECAUSE HAS TO BE SAWED AND SPLIT OUT OF QUARRY NO BLAST ING 5 BASALT GABBRO DIABASE TRAP ROCK BAD BECAUSE IRON MINERALS GIVE A RUSTY STAIN 4 AGGREGATES MIXTLIRES OF MINERAL AND ROCK PAR139CLES A SIzES 1 FINE AGGREGATES PASSES 4 SIEvE 2 coARSE AGGREGATES 475MM 101 MM 4quot 3 OPTIMUM SIZE 127 CM oR 112 quot B CRUSHED AGGREGATE 1 DESIRABLE CHARACTERISTICS A STRENGTH B ABRASIVE RESISTANCE c LOW POROSITY D NO REAcTIvE COMPONENTS E BRlT39LE 2 AGGREGATE PRODUCTION IN THE US CRUSHED ROCK TYPE ToNNAGE VALUE MIL 1 LIMESTONE 146 134 2 39l39RAP ROCK 2o 22 3 GRANITE 18 18 4 MARBLE 4 4 5 sANDsToNE 6 8 6 OTHERS 8 14 3 TRAP ROCK ABUNDANT HERE AND MAKES GREAT AGGREGATE FOR ROAD METAL AND CONCRETE 4 LIMESTONE MOST USED BECAUSE A NOT HARD so EASY To CRUSH B LESS ABRASIVE TO CRUSHING EQUIPMENT c ABUNDANT AND GooD sTRENGTH D NEEDs FOR GooD LIMESTONE AGGREGATE 1 UNIFORM so No IossILs 2 NONPOROUS 3 FREE OF CHERT oRGANIcs AND PYRI3939E C NATURAL SOURCES OF AGGREGATE MAIN SOURCE OF AGGREGATES 1 ALLUVIUM GLACIAL TILL DUNES 2 DO NOT TAKE FROM ACTIVE FLOOD PLAIN OR BEACH D ARTIFICIAL SouRCES 1 CLAY TO BRICKS 2 SLAG 3 INCINERATED URBAN TRASH 4 GLASS 5 FLY ASH 6 SHELLS E USES NONCONCRETE 1 RAILROAD BALLAST WELLGRADED amp NO FINES 2 PARKING LoTS 3 ROCK FILL DAMS 4 BITUMINOUS MIx ASPHALT 5 EMBANKMENTS 6 RoAD METAL NEED CLEAN WELLGRADED A PARTS OF A ROAD SYSTEM 7 FILL BEWARE OF SETTLEMENT WEATHERING AND FROST ACTION 3 RIPRAP A ARMOR NEEDED FOR EROSION FROM WAVES WITH J NO SILICA RICH AGGREGATES CHEMICALLY REACT WITH CONCRETE CA NA K AND OH FROM SETI39ING OF CEMENT COMBINES WITH SILICA TO FORM A GEL WHICH REACTS WATER TO MAKE WEAK 1 SOLUTIONS USE LOW ALKALAI CEMENTS ADD POZZOLANIC CEMENT NO SILICA RICH ROCKS IN AGGREGATE RHYOLITE ANDESITE PHYLLITE TUFF SHALE DACITE CHERT OPAL CHALCEDONY F LIGHT WEIGHT AGGREGATE PRODUCES A DENSITY lt 185 GICC 1 USES LOW WEIGHT NEEDED BY SOME STRENGTH GOOD FOR INSULATION 2 LOW STRENGTH 200 5000 PSI 3 EXAMPLES PUMICE CINDER VERMICULITE CORAL FLY ASH PERLITE pvnw y v 9 A riI39I39r Oxidation Chemically oxidation is the loss of elec trons that accompanies many chemical reactions This results in an increase in positive valency ln weathering the term is usually restricted to the reaction of this type involving oxygen to form oxides or oxygen plus water to form hydroxides Iron oxides and hydroxides typically impart red and yellow staining of rocks and soils Although these colors are desirable for some ornamental purposes their appearance after construction can be a numance The oxidation of iron contained in a mineral crystal lat tice will disrupt the lattice either by collapse or by increasing its susceptibility to other weathering pro cesses Oxidation also occurs after ferrous iron Fe has been released from a mafic silicate by hydrolysis If this ferrous iron enters an oxidizing environment it will form a precipitate containing ferric iron Fe Hydration The addition of water to a mineral struc ture forms a hydrate ln some salts this can have the physically disruptive effect discussed earlier Hydration reactions are particularly important with clay minerals which may incorporate water in their crystal lattices Hydrolysis Water is a dipolar molecule which makes it an active solvent Water usually containing other dis solved ions will displace metal cations from silicate lat tices and lead to the production of new mineral struc tures and compositions Although it represents a gross simplification the following reaction illustrates the results of hydrolysis 2KAlSiO3 3Ho HAlsio 4SiO 2Kquot ZOH Orthoclase Clay Mineral The water often contains acids that aid the process especially carbonic acid The common products of hydrolysis weathering are dissolved silica OH ions aqueous metal cations and clay minerals There is still an incomplete understanding of how hydrolysis combines with other weathering reactions to attack silicate minerals Loughnan 1969 summarizes much of what is known about the leaching of metal cat ions such as Ca Na K and Mg from silicate lattices The process involves surface hydration acid attack entry of water molecules into lattice spaces vacated by cations and eventually the formation of new mineral structures especially clays Winkler 1975 suggests that silicate weathering proceeds rapidly enough to produce discoloring and softening of stone surfaces and even pit ting and crumbling during prolonged exposure to an urban environment The effect is most pronounced in some varieties of basalt y y F ROCK mo STONE AS CONSTRUCTION MATERIALS 135 ROCK AND STONE AS CONSTRUCTION MATERIALS Bates 1960 notes that fc3tJLg eral categgries of mate rials are extracted from the earth for human use 1 met als and metallic ores 2 mineral fuels 3 ground water and 4 other substances particularly industrial rocks and minerals Many of the materials in the latter category are used in construction practice These materials will be dis cussed here because as construction materials they interact closely both with humanity and with geological processes Although the construction industry accounts for over onehalf of the production value of nonmetallic economic rocks and minerals a variety of other non metallics are essential raw materials for other industries They are used in the chemical industry agriculture the ceramics industry as abrasives and as additives for met allurgy Bates 1960 gives an excellent discussion of the occurrence uses economics extraction and processing of these essential earth materials Industrial rock stone and minerals differ in their eco nomics from both metallic ores and mineral fuels Whereas the latter have uniue properties that give them a relatively high that is value per tonne the former generally are valued by their proximity to construction sites Thisl lace valueiresults from the high transportation costs for such bulk materials as building stone sand and gravel or various aggregates for con crete Many of the materials that we will discuss here will be those of high place value Generally in contrast to most materials of high unit value the industrial rocks and minerals are produced in large bulk from widely distrib uted geologic occurrences Processing is usually simple and the materials are rarely imported or exported Building Stone A walk through the older sections of cities in the north eastern United States shows the importance that stone enjoyed in construction prior to the midtwentieth cen tury The famous brownstone homes in New York City were faced with Triassic sandstone quarried from the Connecticut River Valley The importance of building stone in the nineteenth century is exemplified by the transportation of red sandstone from Arizona to Den ver Colorado for construction of the Brown Palace Hotel during the late 1800s Generally however the construction industry uses what is available locally such as granite in Vermont Minnesota Wisconsin and Aber deen Scotland and limestone in Bedford lndiana and Kingston Ontario The Washington Monument in Wash ington DC39 presents a contrasting example of utilization of building stone and transportation costs The first 152 ft 465 m of the monument were built between 1845 V 39 zlEk p 6 LtilciiiKS i frlt Lquot M Z I P z W LU BLof 136 ROCK ITS STRENGTH DURABIUTY AND USES and 1854 with marble from the Piedmont Province quar ries at Texas Maryland just north of Baltimore When funds were depleted construction halted In 1879 work recommeinced on the monument and marble from Lee Massachusetts was used for the next 4 m This marble proved too costly so the remainder of the monument was completed by 1885 using marble from nearby Cockeysville Maryland The distinct color difference between the Texas marble white coarsegrained nearly pure calcium carbonate and the Cockeysville marble pale gray finegrained magnesium rich can be seen in the monument today Since 1945 stone facing has become an expensive decorative aspect of construction Modern buildings emphasize artificial combinations of raw materials glass concrete steel and bakedclay products Nevertheless there is a continuing demand for quality building stone to lend elegance and variety in modern architecture The most important characteristics of building stone are tex ture color durability weatherability and its ability to take polish Building stone is separated from natural rock masses in uarries Figure 520 One basic product is stone lw hich consists of blocks that are mechanically cut to a specified size and shape In urban areas far from rock quarries glacial erratics can serve as a source of dimension stone The Mormon Temple in Salt Lake City Utah was constructed with granite cut from erratics in the glaciated Little Cottonwood Canyon of the Wasach Mountains to the east of the city United States con sumption of dimension stone was 2 million tonnes in I976 The most common lithology of dimension stone in Figure S2O Granite rock quarry at Barre Vermont Photo courtes y or T M Crif rhs I j 4 jj4 l 3939 the United States is granite 37 percent followed by limestone and dolomite 31 percent and sandstone including quartzite 17 percent Table 55 Quarry operations present several hazards as a con sequence of extraction of the resource There are sev eral sources of extreme stress on rock in quarries the most common being the weight of overlying rock and residual tectonic stresses The compressive strength of a freshly quarried rock can be as much as 50 percent less than the same rock aged3939 5 to 6 months following removal from the ground Kieslinger 1967 The expres sion of stress removal or unloading can be rock bumps in the bottom of quarries or the more dangerous explo sive strain release in the free mine or quarry wall known as rock bursts Granite Commercially the term is applied to true granite some gneiss granodiorite and gabbro granites Uniformly colored granite is a highly desirable dimension stone Most of the US production comes from regions where large masses of unweathered gran ite usually intrusive bodies lie at or near the surface These criteria and a proximity to commercial markets make the folded and intruded mountains of New England the southern Piedmont province Georgia and the Carolinas and certain northcentral states Wiscon Table 55 Production of Stone in 1969 by Types of Stone in the United States Percentage of total Type Tonnage Value Crushed stone L39mestone including dolomite 73 67 ranite 9 9 Marble 2 2 Sandstone including quartzite 3 4 W fraprock LL4 Hquot 4via l V 10 11 100 100 Total millions 861 1326 Dimension stone Granite 37 46 Limestone including dolomite 31 18 Marble 4 13 Sandstone including quartzite 17 11 Slate 8 9 Other 3 3 100 39 100 Total millions 1873 599 From US Geological Survey ROCK AND STONE AS CONSTRUCTION MATERIALS 137 sin Minnesota South Dakota the major production centers in the United States Granite quarries usually reveal the distinctive sheet jointing structure that aids the quarrying operation Fig ure 514 Indeed jointing and faulting are critical to the production of dimension stone Too much fracturing produces unusable stone too little makes for difficulties in quarrying Quarry operations are also sometimes impaired by the release of stresses caused by the mining itself On the other hand smallscale deformational structures in a competent rock will sometimes add to the ornamental value Slate The pronounced cleavage of mildly metamor phosed shale called slate made this rock a favorite con struction material in the past Sheets of slate were used as flagstones blackboards roofing shingles and billiard table tops Because of difficulties in quarrying slate requires considerable human labor for its removal Drill ing and blasting would damage the stone so sawing and splitting along the cleavage are used These difficulties have led to such great expense that slate has largely been replaced in many of its traditional uses by other materials Composition roofing has largely replaced the slate roof Nevertheless slate is still valued for its extremely high durability Most slate roofs will outlive the structures on which they are placed Moreover slate has one of the highest tensile strengths normal to the cleavage planes of any rock Sandstone Although sandstone the rock composed predominantly of sandsized quartz grains would seem to be a petrologically simple rock it actually comes in numerous varieties Graywacke contains considerable sandsized grains of rock fragments as well as much finer matrix material Arkose contains greater than 25 percent feldspar Orthoquartzite is greater than 95 percent quartz Variations in cements matrix texture and impurities all contribute to variations in the desirability of sandstone as a construction material Dimension sandstone should have a firm cement of silica or clay Calcite and iron oxide cements can lead to solution weathering or staining Porosity can also cause durability problems as discussed earlier Marble Metamorphosed limestone called marble remains a highly valued dimension stone and a source of memorial or statuary stone Precambrian Georgia marble was used for the statue of Lincoln at the Lincoln Mem orial in Washington DC The John Paul Jones Memorial in the same city is made of Vermont marble The most desirable marble is either uniformly colored or banded Because marble is composed of densely packed inter Q1iJ 0C ja J l8 ROCK lTS STRENGTH DURABIUTY AND USES icked grains it withstands exposure much more readily ian limestone The major US production is from Ver iont and Georgia 09 ilthough the production of dimension stone has ieclined through this century the demand for crushed tone has steadily increased Together with sand and ravel crushed stone is required for such diverse uses s road metal ballast for railroads gravel for parking lots ind driveways aggregate for concrete rock fill dams ind riprap Desirable characteristics of crushed stone for ise in construction are toughness strength abrasive esistance low porosity and absorption and absence of 39eaCtive components In 1950 the value of aggregate Jroduction in the US was about 680 million By 1973 he value adjusted for inflation was over four times as great The 1973 aggregate consumption by the United States was nearly 2 billion tonnes or about 10 tonnes per person per year The US Bureau of Mines 1975 estimates that by the year 2000 the US consumption of aggregate will be 23 billion tonnes The most commonly utilized lithologles for crushed stone in the United States are limestone and dolomite 73 percent followed by basalt and diabase 10 percent and granite 9 percent Table 53 Riprao is irregular broken stone used to protect earth embankments from erosion by waves and stream action Good riprap should have sufficient strength soundness and low water sorption The crushed stone should be angular to allow stability on sloping surfaces lt should be at least 17 cm in diameter and it should have a bulk specific gravity greater than 26 to resist displace ment by waves or currents Basalt and Diabase These rk finegrained igneous rocks known commercially as ltrab rockare highly val ued for concrete aggregate and road material They are drilled and blasted in quarries to produce shattered stone which is crushed and screened before shipment to market This product has a very high place value so sources are located very close to markets usually within 50 km Major production comes from the basalt flows and sills that are intercalated with the Triassic Newark group in the lower Connecticut River Valley northern New Jersey and southeastern Pennsylvania The Colum bia Plateau volcanic province of Washington Oregon and ldaho also provides immense local sources of traprock Irushed Stone Limestone Even the name limestone was derived quotquotquot393939quotquot39 from the commercial use or this rock it was the material used to produce lime as discussed below Limestone includes those sedimentary rocks composed of at least 50 percent calcite and dolomite in which calcite domi nates Like sandstone this rock comes in numerous varieties that reflect complex genetic processes Lime stone is a common rock throughout the Appalachian Pla teaus Allegheny Mountains and Mississippi River Valley Its proximity to major commercial centers has favored its exploitation as crushed stone for road metal railroad ballast and concrete aggregate Limestone is the most heavily used source of crushed stone for aggregate Table 55 Bates 1960 notes that i more than twoand onehalf times as much crushed limestone is used for this purpose as basalt granite and sandstone combined One reason is that limestone is far less abrasive to crushing equipment than these other common rock types However care must be taken that limestone for aggregate be uniform nonporous and free of chert organic matter and pyrite Although not as durable as some dense igneous rocks a quality lime stone usually is resistant enough for most uses of aggre gate Sand and Gravel Sand and gravel accounts for the greatest tonnage of a single resource material that is extracted from the earth This material is basic to modern construction especially as aggregate for concrete permeable subgrades for j roads and railroads bituminous mixes and foundation support The very pronounced place value of this resource results in a need for a close proximity of sup plies to the actual construction sites Cities highway i construction areas and other sites of intense demand will therefore dictate the general location and intensity of sand and gravel extraction The major sources of sand and gravel are alluvial and glacial deposits but locally beach dune and ocean sources are economically available Sand is defined as material ranging in size from 006 mm to 2 mm Gravel ranges from 2 mm to 4 mm gran ules from 4 mm to 64 mm pebbles and from 64 mm to 356 mm cobbles The detailed character of the sand and gravel is designated by gradation or sizedistribu tion curves see Chapter 6 for examples Use of Stone as Concrete Aggregate Concrete is a mixture of aggregate cement and water that hardens after mixing The Romans were pouring concrete over 2000 years ago Aggregate accounts for approximately 70 percent of concrete by volume and l 80 percent by weight therefore its selection for use in 3 ob LwxaMQb I cw concrete is a very important decision Chapter 6 dis cusses several geologic sources for aggregate The American Society for Testing Materials defines a gregate as follows inert materials which when bound together into a conglomerated mass by a matrix form concrete mastic mortar plaster etc Of course no geological material is completely inert and consider able geological investigation is necessary to define and locate materials that will be suitable as aggregate The tegtlttue of a material chosen to be an aggregate is perhaps its most fundamental property Engineers will generally characterize particle size distributions as gradingquot whereas Poorly sorted wide range of particle sizes means the same as well graded The precise description of sedimentary textures will be considered more fully in Chapter 6 Generally a potential material must be clean that is free of fine particles which would include mica clay and organics These impurities could cause a weakened bond between the particle and the cementing agent Some clay minerals will also expand on wetting to pro duce spalling or cracking of the concrete If the potential material contains a predominance of particles in one size class then it may contain considerable void space Then this void space must all be filled with cement to make concrete ldeally therefore the material should be well graded in the sand and gravel range that is it should cohTain an even distribution cTFquotsizes so that finer parti cles fill the voids between the larger ones Often natural materials must be artificially screened and mixed to pro duce an ideal range of sizes to generate the strong cementaggregate bonding necessary for a strong concrete The workability of a cementaggregate mixture is another important consideration in the economics of concrete production Here particle shape will play a role Flat elongated particles tend to make the concrete seg regate because they do not compact as easily as more spherical particles Sharp angular particles require more cement to make the mixture workable Even the surface texture of the particles is important Too smooth a sur face will not promote good bonding between a pebble and the cement Soundn is another important property of aggre gate Actually this is another way of considering weath ering processes both physical and chemical Higl3ly porous or fractured aggregate will readilyabsorb water when being mixed to form concrete Later freezing of this enclosed water could cause expansion and failure of the enclosing mortar Aggregate must never contain nat urally weak or crumbly materials such as migaceous r9cksLshaefriable sandstone and clayey rocks Sulfide minerals such as pyrite and marcasite both FeS will ROCK AND STONE AS CONSTRUCTION MATERIALS I39 oxidize and then hydrate when incorporated into con crete This process produces unsightly staining of the concrete and occasional popouts Sometimes the weak component in an otherwise sound aggregate material is merely a particle coating Coatings of clay silt calcium carbonate gypsum and oxides commonly occur on sand and gravel as a result of natural weathering pro cesses Often such coatings can be easily removed by washing and screening Concrete must be strong and durable Quartz quartz ite and many dense igneous rocks when suitably graded and washed would thus make ideal aggregate Other lithologies can also make fine aggregate but care ful study is necessary prior to a major investment The hardening of cement is a chemical process hydra tion that produces heat and releases alkalies particularly the hydroxTcTes of calcium sodium and potassium The high concentrations of alkalies ieaaict with certain silica rich aggregates to form silicagels which absgrb water from the cement paste and egrt osmotic pressures in the process This pressure creates tensional stresses that exceed the strength of concrete and cairacks and popouts of aggregates increasing the likelihood of freezethaw and water damage Chert is a highly durable rock that might be consid ered a good aggregate for concrete However chert and other cryptocrystalline silicates such as chacedony and opal are some of the worst reactors in concrete Other rock types to avoid as aggregates include rhyolite andesite phyllite shale tuff and silicious limestone The problems of aggregate reactions can be reduced with the use of ow afkai cements less than 06 percent alkali but these cements are more expensive Powers and Steinour 1955 present a useful review and discus sion of the alkali reaction problem in concrete The problem is especially serious for the aggregate industry because chalcedonic quartz is relatively resistant in nat ural weathering environments and therefore is fre quently an important component of stream gravel This natural gravel would otherwise be the most important source of aggregate In areas devoid of aggregate sources artificial aggre gaLe can be created by fusing locally available silt and clay from such sources as loess deposits or harbor and river dredgings The bulk density of normal aggregate is sometimes too great or specialized engineering applications Recent examples include the roadway of the San Fran ciscoOakland Bay Bridge and the floors and walls of the 42story Prudential Life Building in Chicago In these sit uations lightweight aggregate is used to make light weight concrete Lightweight concrete is generally con sidered to be less than 185 gcm H5 lbsft with Wv r1l tLyl 140 ROCK lTS STRENGTH DUR BlLlTY AND USES strengths of 11 to 350 Kgfcm 200 to 5000 psi The loss of compressive strength is compensated by the insulation and weight advantages Some types of light weight aggregates and bulk densities are given in Table 56 Lime Cement and Plaster A cement industry is one of the important ingredients in a modern industrial society Kesler 1976 notes that the annual cement production of some western European countries reaches about threequarters of a tonne per person Because cement presently costs about 20 per tonne it is usually mixed with aggregate to make concrete Lime When limestone and dolomite are heated they lose carbon dioxide CO2 and yield lime CaO CaCO3 heat CaO CO CaCO3 MgCO heat CaO MgO l ZCO3 Production is usually accomplished by he WW 39 g these carbonates in a rotary kil e kiln product is used in plaster and mortar tor the con struction industry and as a source of alkali for the chem ical industry Cement The first lime cements were the natural water limes which after calcining grinding and mixing with water would set to hard cement An example is the Upper Silurian Rondout Formation of eastern New York This unit is a natural mixture of limestone clay and silica During the nineteenth century these natural water limes were the principal sources of industrial cement Today the cement industry relies on Portland cement a pulverized clinker of hydraulic calcium silicates PET land cement is manufactured from lime silica alumina and iron oxides The limestone used for Portland cement must be relatively pure it cannot contain more than 5 percent MgCO3 Dolomites and dolomitic limestones Table 56 Some Types of Lightweight Aggregates Unit Weight lbft kgrn Perlite 612 96192 vermiculite 6 12 96 192 Pumice 3060 480960 Expanded shale 4070 6401120 Cinder 5070 800 1120 Coral 70110 11201760 must be carefully avoided The ideal raw material for Portland cement would be an impure limestone with various oxide impurities in just the right proportions Usually a relatively pure limestone is mixed ay or rotary kiln to produce a glassy clinker cates and aluminates When mixed w ket consideratio dictate the placement of plants close to large cities ypsum and Plaster Gypsum CaSO 2H2O is ommonly called g L er of paris This material can be mixed with water and spreTiTTt then sets to a dense mass of fibrous gypsum crystals forming excellent lath and wallboard Clay Bricks and Sand lCeramics were one of the first materials that humans synthesized from their environment Prehistoric people f an easily worked mixture of clay and water w as useful products Bricks were used as early as 6000 for construction at Jericho Davey 1961 Today the industrial uses of ceramics include various bricks drain tiles sewer pipes and architectural terra cotta Refrac rores are heatresistant agents that are used to line fur naces and to act as fire barriers Because of low cost and abundance many forms of clay and shale serve as raw materials for a broad spectrum of ceramic products The technology of these industrial clay products is reviewed by Brownell 1976 Clay and Shale Clay is one of the most important earth materials The term clay refers both to 1 detrital particles smaller than about 2 u and 2 clay minerals Actually clay minerals dominate in the finer size classes so there is overlap in the definitions Clay is character ized by its ability to form a pasty plastic moldable mass when mixed with water The physical properties of clay minerals will be discussed in more detail in Chapter 8 Ceramic clay products include industrial items such as brick construction tile and pipe and kiln products such as pottery chinaware porcelain and highgrade tile Bates 1960 estimates that 75 percent of all commercial clay and shale find use as ceramics Quality kiln products n are usually made from clays high in the mineral kaolinite see Chapter 8 This material has the desirable proper ties of 1 high plasticity when wet and 2 low shrinkage plus high strength on drying The purer kaolin clays are also extensively used in the production of paper rubber paint plastics pharmaceuticals and chemicals United States production exceeds 2 million tonnes annually The various uses of clay fall in four categories refrac tories cementju ghtweight aggregate and heavy clay products The uses of cement and aggregate have already been discussed The heavy industrial or struc t 39 39i clay products are made with more common clays and shales composed of mixed clay minerals and impur ities iron oxide provides a useful flux lowering the tem perat rticles fuse together to form a tightly bound mass Fire clays differ from other ceramic clays in that they are required to withstand higher temperatures before melting Generally the high alumina clays kaolinite gibbsite and diaspore havet lTe highest melting temper amTeTSometimes however high refractoriness resis tance to melting coincides with low plasticity Nonplas tic fire clay called flint clay Fhust be mixed with plastic clay to become useful The commonly used rotary system of drilling for petroleum requires a colloidal mud to lubricate the bit lift rock cuttings from the bottom of the hole and pro tect the hole walls An ideal material for this purpose is devitrified volcanic ash bentonite rich in the clay min eral sodiummontmorillonite Bentonite is also used as a binding agent for the sand molds employed at foundar ies as a gL als and insecticides and in a host of specialized industriafapplications Indeed new applications of clay minerals are the subject of consid erable active research Grim 1962 provides a useful 39eview of this work Sand and Sandstone Sand or weakly cemented sand tone that is high in quartz content is most valuable for BOUFCES of foundry molds glass refractory stone filter ng medium and abrasives Some uses make certain sand ypes sufficiently valuable to give them a high unit value oundr sand used for making molds for molten metal nust have the following properties Bates 1960 1 suf icient cohesiveness often clay bonds to hold together vhen moist 2 sufficient ability refractoriness to with tand metal pouring temperatures as much as 1SOO C or steel 3 sufficient strength 4 sufficient permeabil y to permit gases to escape from the cooling metal and quotii a texture and composition that will not interact with rat metal Class sand requires an extremely high quartz content gt93 percent Usually othoquarrzites gt95 percent ROCK AND STONE AS CONSTRUCTION MATERlALS 141 quartz sands are sought Even small amounts of certain impurities such as iron oxide will discolor glass The Ordovician St Peter Sandstone of Minnesota Wiscon sin Iowa Illinois and Missouri is an example of a remark ably widespread orthoquartzite that can easily be used for glass production SUMMARY Rock and stone engineering characteristics are deter mined by standard tests established by the American Society for Testing and Materials Common tests include bulk specific gravity porosity water absorption dura bility hardness abrasion toughness and soundness Stress is measured as a force per unit area that devel ops within rock to resist external forces Any resulting deformation is defined as strain Rock strength is mea sured by compression and tension tests where a force is applied to a cylinder of rock until the sample fails Many factors contribute to rock strength including tex ture structure mineralogy moisture content and degree of cementation Tensional strength of rock is typ ically only about 10 percent of the compressive strength When a linear relationship exists between stress and strain the rock acts as an elastic material Plastic mate rials do not deform until a threshold stress is exceeded The Mohr Coulomb theory of failure indicates that the shear stress at failure is defined as r 0 tan 1 10 where T critical shear stress 0 normal stress in angle of internal friction and To cohesion Discon tinuities such as faults joints foliation and bedding greatly affect the strength of rock Stone used in construction is subject to weathering This is accomplished by water carbon dioxide aerosols salts and other atmospheric gases such as S0 and S03 Moisture and salts are the most damaging to stone Weathering processes include solution carbonation oxidation hydration and hydrolysis Unlike metallic ores and mineral fuels which have a high unit value rock and stone have low unit values but high place values because of high transportation costs Since 1945 there has been a shift from stone to glass concrete steel and clay products as construction mate rials US consumption of dimension stone was about 2 million tonnes in 1976 primarily granite limestone dolo mite sandstone and quartzite Crushed stone is used for road metal railroad ballast aggregate for concrete fill and riprap Limestone and dolomite are by far the most commonly used rock types Sand and gravel represent the greatest tonnage of any resource extracted from the earth The largest use is as aggregate in concrete Good aggregate should be free of fines wellgraded and not too angular nor too 142 ROCK lTS STRENGTH DURABJLJTY AND USES rounded Finegrained silicates such as chert and opal and some silicarich igneous rocks react chemically with cement and should be avoided Clay is used in bricks tile pipe pottery and china Kaolinite clay is used primarily in ceramics bentonite is used for drilling mud and many specialized industrial uses Sand and sandstone deposits with 93 percent or more silica quartz are needed for glassmaking REFERENCES AND SUGGESTED READINGS Attewell P 8 and Farmer l W 1976 Principles of engineer ing geology Chapman and Hall London 1045 p Bates R L 1960 Geology of the industrial rocks and minerals Harper 8 Row New York141 p Bieniawski Z T 1967 Mechanism of brittle fracture of rock part I theory of the fracture process lnternat Jour Rock Mechanics and Min Sci v 4 p 395407 Birkeland P W 1974 Pedology weathering and geomor phological research Oxford Univ Press New York 285 p Blackwelder E 1925 Exfoliation as a phase of rock weather ing Jour Geology v 33 p 793806 h Brace W F 1960 An extension of the Grif th theory of frac ture to rocks Jour Geophys Res v 69 p 34493456 Brownell W E 1976 Structural clay products SpringerVer lag New York 231 p Carroll D 1970 Rock weathering Plenum Press New York 203 p Cooke R U and Doornkamp J C 1974 Geomorphology in environmental management Oxford Univ Press London 413 p Cooke R U and Smalley l J 1968 Salt weathering in deserts Nature v 220 no 1 p 226227 Coulomb C A 1776 Essai sur une application des regles de maximis et minimis a quelques problemes de statitique rela tifs a l39architecture Acad Royale Sci Paris Mem Math PhyS v 7 p 343382 Correns C W 1949 Growth and dissolution of crystals under linear pressure in Disc Faraday Soc No 5 Crystal growth Butterworth London p 267271 Davey N 1961 A history of building materials Camelot Press London 260 p Deere D U 1968 Geological considerations in Stagg K G and Zienkiewicz O C eds Rock mechanics in engineering practice John Wiley and Sons New York p 120 Deere D U and Miller R P 1966 Engineering classi cation and index properties for intact rock US Air Force Weapons Lab Tech Report AFWLTR65116 Kirtland Base New Mexico Dunn J R and Hudec P P 1966 Water clay and rock soundness Ohio Journal of Science v 66 p 153167 E 305 L 5 1970 Salt crystallization and rock weathering a review Revue de geomorphologie dynamique v 19 no 4 p153177 39 Farmer l W 1968 Engineering properties of rocks E and F N Spon Ltd London 180 p Feld J 1965 Rock as an engineering material Soiltest nc Evanston lll 32 p Flawn P T 1970 Environmental geology Harper 8 Row New York 313 p Garner L E 1976 Aggregate resource conservation in urban areas Univ Texas Bur Econ Geology Research Note 4 12 p Gauri K L 1973 The preservation of stone Scientific Ameri can v 238 no 6 p 126136 Gilbert G K 1904 Domes and dome structures of the High Sierra Geol Soc America Bull v 15 p 2935 Goudie A Cooke R U and Evans l 1970 Experimental investigation of rock weathering by salts Area V 1 no 4 p42 48 Griffith J H 1937 Physical properties of typical American rocks Iowa Engr Expt Sta Bull 131 61 p Griggs D T 1936 The factor of fatigue in rock exfoliation Jour Geology v 44 p 783796 Griggs D T 1939 Creep of rocks Jour Geology v 47 p 225251 Grim R E 1962 Applied clay mineralogy McGrawHill New York 422 p Hockman A and Kessler D W 1950 Thermal and moisture expansion studies of some domestic granites US National Bureau of Standards Research Paper 2087 v 44 p 395 410 Hubbert M llt 1951 Mechanical basis for certain familiar geo logic structures Geol Soc America 8ull v 62 p 355 372 Hubbert M K and Rubey W W 1959 Role of fluid pres sure in mechanics of overthrust faulting Geol Soc America Bul v 70 p 115166 laeger J C 1964 Elasticity fracture and flow Methuen and Company London 212 p Judd W R 1959 Effect of the elastic properties of rock on civil engineering design in symposium on rock mechanics P D Trask ed Geol Soc Amer Engineering Geology Case Histories No 3 p 5576 Keller W D 1957 The principles of chemical weathering Lucas 8ros Columbia Missouri 111 p Kesler S E 1976 Our finite mineral resources McGrawHill New York 120 p Kieslinger A 1967 Residual stress Summary Proc 1st Con gress lntern Rock Mechanics lll p 354357 Krynine D P and Judd W R 1957 Principles of engineering geology and geotechnics McGrawHill New York 730 p Loughnan F C 1969 Chemical weathering of the silicate min erals Elsevier New York 154 p McLintock D and Walsh J 8 1962 Friction on Griffith Cracks under compression Proc 4th Natl Congr Appl Mech Berkeley p 10151021 Mohr O C 1882 Uber die Darstellung des Spannungszu standes und des Deformationszustandes eines Korperele mentes und uber die Answendung derselben in der Festig keitslehre Der Civilingenieur v 28 p 113156 Obert L and Duval W l 1967 Rock mechanics and the design of structures in rock John Wiley and Sons New York 650 p Ollier C D 1969 Weathering Elsevier New York 304 p Powers T C and Steinour H H 1955 An interpretation of some published researches on the alkaliaggregate reaction GROUNDWATER AND ENGINEERING A GROUNDWATER THIRD IMPORTANT THING FOR THE ENGINEERING GEOLOGIST TO LOOK FOR SOIL ROCK WATER IMPAIRS FUNCTION OF DAMS LEVEES CANALS SHORTENS LIFE OF ROADS RUNWAYS CAUSES LANDSLIDES AND FOUNDATION FAILURES THEREFORE CONTROL IMPORTANT LEAVE EXPLORATION AND DEVELOPMENT TO OTHERS B OCCURRENCE OF GROUNDWATER IMPORTANT TERMSIMUST DESCRIBE FOR FOR THE SITE 1 2 3 4 5 6 397 8 VADOSE ZONE ZONE OF AERATION PHREATIC ZONE GROUNDWATER ZONE OF SATURATION MOST IMPORTANT FOR EG PROBLEMS HERE WATER TABLE LINE BETWEEN ZONES UNCONFINED AQUIFER WATER BEARING UNIT WITH VADOSE ABOVE PERCHED AQUIFER BIG PROBLEM OF EG IMPERMEABLE zONE IN THE VADOSE zONE CONFINED AQUIFER IMPERMEABLE LAYER OVER THE AQUIFER ARTESIAN SYSTEM PIEZOMETRIC SURFACE SURFACE To WHICH WATER WILL RISE ABOVE CONFINED AQUIFER PERMEABILITY DARCY39S LAW A BEST IF MEASURED IN FIELD HIGHLY VARIABLE IN LAB B FT3FT2DAY FT3FT2MIN CALFT2DAY M3M2DAY C VERY HIGH CLEAN CRAVEL To VERY LOW CLAY D WANT TO DETERMINE PERVIOUS SEMI PERVIOUS IMPERMABLE 9 HYDROSTATIC PRESSURE PORE PRESSURE IN SOIL WHEN WATER IS MDTIONLESS PIEZOMTER 10 HYDRAULIC GRADIENT IF ONA SLOPE PIEZOMTERS SHOW DIFFERENT VALUES ENERGY LINE IS SLOPED WATER FLOWS TO LOW ENERGY POINT SEEPAGE PRESSURE 11 GROUNDWATERAFFECTS RESPONSE OF SOIL MASS TO APPLIED LOAD A UNSATURATED GROUND INTERGRANULAR PRESSURE GRAINS RESIST COMPRESSIONAL PRESSURE 1 EFFECTIVE STRESS B SATURATED GROUND WATER FILLING VOIDS CANNOT BE COMRESSED SO 1 TOTAL STRESS EFFECTIVE STRESS PLUS HYDROSTATIC PRESSURE SO STRONGER IN COMPRESSION 2 WATER NO SHEAR STRENGTH SO ABILITY OF SOIL TO RESIST SHEAR STRESS IS LOW C LONGTERM STABILITY OF CUTS AND FILLS LOW 1 CLAYS HIGH PERMEABILITY HIGH WATER D SEEPAGE PRESSURE FORCEUNIT VOLUM OF SOIL ON FREE FACE DISLODGES PARTICLES PIPING C ENGINEERING SIGNIFICANCE 1 PROBLEM TO CONSTRUCTION A IF DIGGING HOLE WATER INTO HOLE SO THEREFORE MUST DEWATER SYSTEM BEFORE CONSTRUCTION 1 GRAMBLING STADIUM MISSISSIPPI DAM B MAY CAUSE WATER TO FORM QUICKSAND NORTH DAKOTA 2 ACTING AS EROSION AGENT THAT DEGRADES STRUCTURE A BOILING AND PIPING NEEDS INITIAL FRACTURE JOINT ANIMAL BURROW UNPLUGGED DRILLHOLES 1 TETON DAM DAM IN COLORADO B LANDSLIDES RAPID DRAWDOWN OF LAKERIVER 1 LEVEE OR SLOPE FAILS HIGH SATURATED WEIGHTS AND LOW SHEAR STRENGTHS 2 ALSO FROM HIGH RAINFALLS C UPLIFT PRESSURES AS PORE PRESSURE UP MALPASSET DAM DISASTER SE FRANCE 3 AFFECTING FUNCTIONING OF STRUCTURE A FLOODS RAIL AND CAR TUNNELS NEED PUMPS TO REMOVE WATER B SEEPAGE CONTROL OF SURFACE IMPOUNDMENTS DON39T WANT IT TO LEAVE IRRIGATION CANALS WASTE LAGOONS TAILING PONDS 4 MEDIUMFOR CONTAMINANT MOVEMENT IF THE SYSTEMS LEAK ONE MUST UNDERSTAND FLOWS TO MONITORMOVEMENT MONITOR WELLS A ONE WILL HAVE TO DEVELOP LOCATIONS AND DEPTHS FOR MONITORING WELLS BASED ON SUBSURFACE FLOWS WATER TABLES ETC D CONTROL OF SUBSURRACE WATER CHOOSING TYPE DEPENDS ON TYPE OF ENGINEERING INVOLVED SITE CONDITIONS AND PURPOSE FOR CONTROL 1 BARRIERS TO REDUCE QUANTITY AND VELOCITY OF SUBSURFACE WATER A OFTEN PART OF THE STRUCTURE B SHEET PILE CUTOFF WALLS BEST FOR COARSE GRAINED SEDIMNTS ESP IF STRATIFIED WITH PERVIOUSIMER DON39T WANT BOULDERS IN THE SOIL C IMPERVIOUS CUTOFF TRENCH COMPACTED MATERIAL IN TRENCH D GROUTED OR INJECTED CUTOFF CURTAINS USED WHERE ABOVE TWO CAN39T GO THAT DEEP E FREEZING OF SLOPE EXPENSIVE ONLY FOR SHORT TIME 2 LINERS TO PREVENT SEEPAGE FROM CANAL IMTOUNDMENT WATER OR WASTES IN WATER A BURIED PLASTIC LINER PUT ON SOIL IN GRAVELLY B BURIED SYNTHETIC RUBBER LINER USUALLY COMBINED WITH POLYESTER REINPORCEMENTS C BENTONITE SEAL SWELLING CLAY SEALS RESERVOIR LEAKS CAN SEAL SOILS COMPACT D EARTH LINING CLAY RICH B HORIZONS 24 FT THICK E THIN COMACTED SOIL LINING WITH CHEMICAL DISPERSANT SEALER SoDIUMTETRA PHOSPHATE REDUCES SOIL To 1 FOOT IF SEALER PUT ON TOP 3 DRAINS REDUCE QUANTITY OF WATERAND DIRECT ITS MOVEMENT A IMPORTANT DON39T LET FINES GET INTO DRAIN 1 CLOGS DRAIN AND STARTS PIPING B USE EQUATION ON P 231 SIZING OF DRAIN MATERIALS C ALSO USE GEOTECHNICAL EABRICSFILTER CLOTHS ALLOWS FINES TO CROSS IT THAT WILL BE REMOVED BY WATER BUT LARGER ONES THAT WILL CLOG IT39WILL NOT CROSS D TYPES OF DRAINS 1 BLANKET DRAINS BETWEEN SUREACE AND BOTTOM 2 INTERCEPTOR DRAIN EXCAVATION FILLED39WITH DRAINAGE MATERIAL CATCH AND REDIRECT FLOW THE 4 DEWATERING THE SITE USE WELLS TO ELIMINATE GROUNDWATER A SUMP COLLECTION TRENCH DEEPER THAN PROTECTED AREA B C D E F 1 AS WATER COLLECTED IT IS PUMPED AWAI SO DRAWS DOWN THE WATER TABLE WELL POINTS DRILLED TOA SHALLOWER POINT AND PUMP WATER OUT LOWER39WT PUMPING WELLS DEEPER THAN WELL POINTS JUST LIKE NORMALWELL RELIEF WELLS VERTICAL INTERCEPTOR DRAIN IN ARTESIAN AQUIFERS USED TO DEWATER DURING CONSTRUCTION TO RELIEVE UPLIFT PRESSURE ON FOUNDATIONS HORIZONTAL WELLS GRAVITY TO REMOVE WATER ESP IN LANDSLIDES 1 MUST DETERMINE FAILURE PLANE AND DIRECTION OF WATER FLOW EXAMPLES OF MISSISSIPPI RIVER AND GRAMBLING STADIUM MODULE 51 Plezometer open stand pipe 3 Piezometric Level I 7 W A 2 Elevation Baseline 1 ll Compute total head 1 and porewater 2 Porewater pressure pressure p at point A when ru hp yw hp 532 meters la 532 meters X 98 Z 2466 Di1 f fS kilonewtonscubic meter kNm3 32 98 kilonewtonscubic meter u 521 kilopascals kPa 1 Total head hz h 2466 meters 532 meters h 25192 meters 2 3 5396 1000 0 co I a5 a 39 A Dbv X iaztq 39quot l39 AI lquot39 4Iun39 39 u v rquotJ quot u u 3 i J 1 l i Static wetter level Sump pumps Trench sumps 777 77 7if7WW177277I a Static water level Well points Pumping water level IIIIZII Ir39lIl3 b Figure 59 Examples of wells a A system of sumps to dewater an excavation b A set of well points protecting an excavation in a similar setting From USBR 1981 lt2 I id r s g r4 Y uLquot quot3 39 r nrrr3939 quot t 39 39 g 4 39 39lt3939 Frquot quot11 quotquotquot3939quot n quot r39 4 3 397r 4 4 o trfl u ix u 397quotquotquot 3939 2 139 39339quot 0 rs 39 v r 4r39 quot 39 ll r w rrv39 1 39 lt r 39 W 4 Instrumentation A Introduction 1 Need preconstruction construction post construction in situ 2 What measured a defonnation of earth material surrounding openings b slope movement c earth induced loads on structures d structural loads on earth materials e pore water pressure in soillrock f stresses in rocks 3 Placement of instruments with regard to a orientation of tectonically caused stress elds b distribution of discontinuities c differences in rock types during construction d groundwater conditions and drainage differences e soil differences 4 Steps see 14 steps on page 264 B Instrument types and applications all measure defonnation or movement electrically or by resistance or inductance 1 Loads used esp During construction A Uses measure structural loads on mineltunnel supports rock bolts see if load is good for design B lnstrIIments load cells resistance type induction type photoelastic type mechanical type 1 want to determine abutment load zone time time to transfer load from ceiling to walls through steel supports once transferred replaced with shims 2 Pressures during amp after construction A uses 1 pressures in earth embankments during construc vertical or lateral pressures on retaining walls 2 pressure on concrete tunnel linings in form of extemal rock loads 3 internal pressures in waterpressure tunnels 4 under earth dams contact of soil B need compressibility of cell must be same as material it is in not more rigid or less C instruments operate hydraulically ie Tubing 3 Axial deformation strain measures changes in length along an axis borehole A uses 1 differential settlements in materials 2 differential strains on unstable slopes 3 changes in interior diameter of a tunnel B instrument extensometer 1 MPBX multiple position borehole extensometer many sites in borehole so variable strain mounted into walls of tunnels 4 Lateral Deformation defonnation perpendicular to axis of borehole monitor stability of hole transverse A uses defonnation in tunnels shafts embankments dams foundations B de ectometer or transverse extensometer orientation in space open pit mines dam abutments excavations 1 put into stable rock know plane of de ection like wall coming out measure de ection C inclinometer into vertical borehole deviations in the vertical 1 esp On active landslides slip surfaces 2 others lateral displacement of earth dams amp embankments 3 sensing probe down installed plasticlaluminum tube measure periodically 4 multisensor unit when continuous monitoring needed sensors at selected depths more expensive A can set alann when max Displacement is reached landslides excavations pits 5 can see zone of failure in landslide 6 can use shear strips as multisensor grouted in drillholes 5 Rotational Defonnation movement ti tmeter rotationltilt A uses lava into volcano slopes subsidence over tunnels dam abutments defonnation following tunnel and mine operations B instrument mounted in rock face gravity activated monitored periodically or continuously 6 Pore Water Pressure Piezometers A measures water pressure at a given point hydraulic head B open type Casagrande type tube into ground 1 can sample depths of water table pressures at depths amp can sample water C closed hydraulic amp pneumatic piezometers closed with membranes D why effectiveness of dewatering during excavations and slope stabilization foundations of earth dams sanitary landfills LECTURE ON EXPLORATION 1 MAPS 2 REMOTE SENSING IMAGE OF EARTH S SURFACE FROM ON HIGH PLANE SATELLITE A MUST GROUND TRUTH ALI REMOTE SENSING B AIR PHOTOS 1 BLACK amp WHITE CHEAPEST 2 COLOR BEST WHEN VEGETATION CONTRASTS IN FAIL OR WINTER 3 COLOR IR INFRARED WORKS WELL IF WANT WATER DIFFERENCES IN SOIL amp ROCK LIKE SPRINGS 4 GET THREE DIMENSIONS A LOOK FOR LINEATIONS FAULTS B PROCESS LANDSLIDES MORAINES TERRACES DUNES PERMAFROST C PAST HISTORT IF SEQUENCE OF PHOTOS 1 EROSION QUARRIES PAST LANDUSE C MULTISPECTRAL SCANNING IMAGERI MAINLI SATELLITE DERIVED MSS LANDSAT 39 N0 DISTORTION DIGITAL FOR ENHANCEMENT NO 3 D 1 SPECTRAL 5 THERMAL SCANNERS A BEFORE 1982 4 BANDS 18 DAY CYCLE 80 M RESOLUTION B AFTER 1982 7 BANDS 30 M RESOLUTION 2 COMBINE BANDS AND GET INTERESTING IMAGES 3 BEST FOR BIG PICTURE TECTONICS LI S EDGES OF LANDSLIDES amp MDISTURE VEGETATION SOILS ROCKS OIL EXPLORATION D THERMAL IR LANDSAT MSS 1 PICKS UP DIFFERENCES IN TEMERATURE ON BANDS BEST FORMOISTURE DIFFERENCES SEEPS FAULT BOUNDARIES DRAINAGE PATTERNS GROUNDWATER FLOW LITHOLOGY amp SOIL DIFFERENCES E MICROWAVE LANDSAT MSS 1 PASSIVE EXTENSION OF THERMAL IR FOR SOIL MOISTURE KARST MINED AREAS F RADAR SLAR SIDELOOKING AIRBORNE RADAR 1 SEES THROUGH CLOUDS 2 BIG FEATURES OVERLOOKED BY BIG BUSY PATTERNS PICKS UP MOISTURE DIFFS SURFACE ROUGHNESS VEGETATION 3 PROBLEM RESOLUTION POOR G TERRESTRIAL PHOTOGRAMETRI STEREO PHOTOS FROM HORIZONTAL CAMERAS 1 MAP DISCONTINUITIES ON OPEN PIT MINES DAM ABUTMNTS DOCUMNT ROCK 5 SOIL MOVEMNTS H GROUND PENETRATING RADAR RADAR INTO GROUND FROM SMALL RADAR UNIT PORTABLE GIVES cROSS SEcTION OF UNDERGROUND UNITS 3 SUBSURFACE EXPLORATION A DEFINE SUBSURFACE CONDITIONS 1 THICKNESS OF SOILS ROCK TYPES EAULTS GROUNDWATER VERTICAL AND LATERAL EXTENTS OF ABOVE 2 DIRECT AND INDIRECT M2E39ASU39REMENTS B EXPLORATORY ExCAvATION BEST WAY BUT COSTLY DISTURBS GROUND 5 CAN39T GO DEEP amp NEED SHORING BELOW 5 FEET 1 HAND EXCAVATED TRENCH 2 BACKHOE ExCAvATED TRENCH 3 DOzER ExCAvATED TRENCH 4 FAULT TRENCH ACROSS THE FAULT 5 QUARRY WALLS ROAD CUTS RIVER CUTS BEST 5 FACE MAPPING GREAT DEAL OF DISCONTINUITIES 6 BEST SAMPLING 397 OSHA quotCONSTRUCTION EXCAVATION RULESquot A CLASSIFI SOIL 1 STIFF SOIL CLASS A 2 INTERMEDIATE SOIL CLASS B 3 NONCOHESIVE SOIL CLASS C 4 ROCK B TRENCH DESIGN 1 CLASS ASOIL 341 SLOPESBENCHES SLOPED SIDES WSHORES 2 CLASS B SOILS 11 SLOPES 3 CLASS C SOILS 151 SLOPES C SHORES HYDRAULIC ALUMINUM SHORES EVERY 6 FEET RAMS TOP 2 FT FROM SURFACE amp BOTTOM 2 FT FROM BOTTOM 1 COSTS 650WEEK FOR 15 sHoREs EDR 100 FT TRENCH D WEAR HARD HAI E LAID BACK TRENCH BETTER cosrs LEss amp GAH KEEP OPEN EoR ONGER MDRE COSTLY TO DIG EASIER TO GET LIGHT IN EDR PHOTOS CAN DIG INTO IT NEED LARGERAREA F NEEDS NAILS SAMPLE EAGs SHORING LADDERS FLAGGING SAFETY FENCES HARD HAIs STEEL TOED BOOTS TAPES sH0vELs scRARERs PUM TARPS GAMERA LUMBER TO covER TRENCH G ExcAvAIIoH EoR 100 FT TRENCH 1 100 TO MDBILIZE 90HR 1 DA 2 5 DAY TO FILL IN amp MDEILIEAIIGH 3 TOTAL 1300 H NEED IHsuRANcE EDR you AHD DIGGER I c0MRAcII0H OR FILLING IN RESEED c BOREHOLE EHDAVAIIDN 1 CORING EASTER amp GHEARER THAN DRILLING WHERE TRENCHING CAN39T BE DONE HIGH WAIER oRwEAH SEDIMENTS A BUCKET AUGER Go0D TO 15 FT 8quot SEGMEHIG B GOUGE coRER THIN amp MAIHLY FOR BOGS C39VIBRACORE CONTINUOUS coRE FROM SAND 34quot ID DOWN 2039 IN MUCK ONLY FOR UNCEMENTED SAND SILT CLAY NO GRAVELS 23 MENUTES TO VIBRATE IN amp WINCH OUT COMERCIAL1000DAY FOR 45 SITES D RAM CORING SHELBY TUBES GIDDINGS FROM TRUCK OR SLEDGE HAMMER34quot DIAMETER PVC OR ALUMINUM E BOX CORER FRO BOAT USED TO CHARACTERIZE DEPOSITIONAL ENVIRONMENT OF WATER BOTTO40quotW F BENTHOS GRAVITY CORER OFF BOAT UP TO 350 LBS OF WEIGHTS GRAVITY CORER OUT WITH WINCH 3 M IN MUDS 1 M IN SANDS 24quot D G PISTON CORER OFF SHIP UP TO 50 FT CORE SUCKS SAMPLE INTO TUBE 24quot D 2 DRILLING DEEPER PENETRATION SAMPLING CASINGS SOMETIMES THREADED PIPE amp SPINS A MAKE SURE LOCATE UTILITIES BEFORE DRILLING AT EACH SITE B AUGER THREADS ON DRILL BIT ARE TURNED TO BORE HOLE YIELDS CUTTINGS ON THREADS 1 CAN REPLACE DRILL WITH SHELBY TUBES amp RAM THEM 3quot X 20quot 2 CAN39T CASE 3 WORKS WELL IN COHESIVE SOILS BUT NOT C D E SANDS PRONE TO HOLE COLLAPSE IN SANDS 4 DOWN TO 150 ft HOLLOW STEM AUGER HOLLOW STEM BIT l5m ACCEPTS 10 cm DIAMETER CORE IN PLASTIC LINER SEQUENTIAL CORING YIELDS NEARLY CONTINUOUS CORE WORKS WELL IN COHESIVE SOILS NOT GOOD FOR SANDS AND GRAVELS PRONE TO HOLE COLLAPSE E BIT BINDING MAX DEPTH 100 FT CAN39T CASE 1500DAY amp MOBILIZATION TWO DAYS FOR 100 FT CABLE TOOL SPLIT SPOON CORE HEAD IS DRIVEN BY FREE FALL WEIGHT SPT CURVE SMALL AMOUNT OF SAMPLE INTO JARS EACH 10 FT WORKS WELL IN COHESIVE SOILS OFTEN REQUIRES CASING OFTEN USED FOR GROUND WATER CONTAMINATION STUDIES NO MUDS USED amp CASING ELIMINATES AQUIFER CONTAMINATION TO 100 FT NEED TO CASE ROTARY AIR AIR COMPRESSORS FORCE AIR DOWN DRILL STEM amp OUT TRICONE BIT CU I39TINGS UP HOLE ESTIMATED DEPTHS CAN REPLACE BIT WITH ROCK CORE BIT IF HIT ROCK WATER WELL DRILLING FAST 300 ftDAY 1000DAY F MUD ROTARY SOIL FOUNDATION TESTS GETS CONTINUOUS CORE IF WANT MUD AS LUBRICANT so CONTAMINATED CAN CASE CAN ALSO DO WITH CUTTINGS amp CATCH CUTTINGS ON MUD SCREEN 10039DAY NEED MUD POND MOST MUDS BENTONITESBARITE ZEOLITE IF SALT WATER As BENTONITE FLOCCULATES G WATER ROTARY HARD ROCK MINING H CASINGS DOUBLES TIMES amp COSTS STEEL amp PVC I COSTS TO 10039 20FT SAMPLING ABOUT 1000DAY MOBILIZATION amp STANDBY FEE 3 CONE PENETROMETER HOW MUCH PRESSURE TO PUSH CONE INTO GROUND STRAIN GAUGE amp PIEZOMETER AT END FRICTION SLEEVE ON OUTSIDE TO 150 FT CAN GET SHEAR WAVE VELOCITY PRESSURE TONSCM2 AND FRICTION BETTER RESOLUTION 1000DAY 23 50F39I39 HOLES NOW 23 HERE IN PNW BAD NEWS NO SAMPLES FOR EINE SAMPLES 9 MOISTURE STRENGTHS OVERCONSOLIDATION RELATIVE DENSITY D GEOPHYSICAL INDIRECT METHODS SUPPLEMENT EXCAVATION AND BOREHOLE DATA 1 SEISMIC PROPAGATION OF SHOCK WAVES P amp S WAVES 7 PROPERTIES OF THE WAVE VELOCITIES HAMMER ExPLOSIVES WEIGHT A EACTORS CRYSTALLINITY V GOES UP B EACTORS POROSITY CLAY 9 DISCONTINUITIES WEATHERING FOLIATION amp JOINTS UP THEN V C D E F GOES DOWN REFRACTION ACCURATE DEPTHS USES FIRST ARRIVAL OF39WAVES BURIED SOIL AND ROCK LAYERS DEPTH TO BEDROCK LANDSLIDE SLIP SURFACES amp VOLUMES USED ALOT IN SHALLOW ENGINEERING EASIER CHEAPER REFLECTION USES LAST ARRIVAL OF WAVES ACOUSTIC SARN SUBAUDIBLE ROCK NOISE USED IN LANDSLIDE ANALYSIS CRACKSHR GIVES RATES OF MOVEMNT ELECTRICAL IONIC CONDUCTANCE RESISTANCE TO CURRENT FLOW 1 GIVES MINERALOGY TEXTURE WATER 2 NEED TO COMPARE TO STANDARD 3 CHANGE OVER TIME 4 FILL IN BETWEEN BORE HOLES 5 LANDSLIDE BOTTOMS G 470570 T ERRAIN MODELS LECTURE 1 PREDICTION A QUESTIONS TO ASK 1 PROCESSES AFFECT STRUCTURES A SUITABILITY OF THE LOCATION 2 HOW STRUCTURES ALTER THE PROCESSES B RISK 1 ENG GEOL OBJECTIVE WHAT IS THE RISK 2 OWNER AND PLANNER SUBJECTIVE WHAT IS THE ACCEPTABLE LEVEL OF RISK YOU CAN ALWAYS PUT UP WITH SOME RISK 2 ICE PROCESSES CLIMATE AND FREEZING OF WATER IN SUBSTRATE A HOW PROCESS AFFECTS STRUCTURES FROST HEAVING 1 DEPTH OF FREEZING OF THE LOCAL AREA FOR PIPES 2 ROADS AND WALLS KEEP POROSITY LOW SO WATER DOES NOT FREEZE AND CAUSE TO BREAK UP 3 ICE ON LAKESIRIVERS WILL AFFECT THE DAMS AND POOLS WHEN IT EXPANDS DESIGN STRUCTURES FOR THIS A ICE DAMS IF ICE FORMS WILL IT DAM RIVER 4 WATER SUPPLY SITING OF DAMS IMPORTANT SO CAN HAVE WATER IN WINTER B HOW STRUCTURES AFFECT PROCESS 1 PERMAFROST VEGETATION MATIACTIVE LAYERIPERMAFROST A BREAKING VEG MAT FORMS LAKE B HIGHWAYS INSULATE C PIPELINES IF HOT LIKE ALASKA PIPELINE 165F 1 WET PERMAFROST ABOVE GROUND 2 DRY PERMAFROST BELOW GROUND ax COST D PIPES IN TUNDRA MELT THE PERMAFROST so PUT ABOVE GROUND AND INSULATE E BUILDINGS BUILD ON STILTS so DOES NOT MELT IT F DAMS AND SEWAGE TREATMENT PLANTS DIFFICULT 3 STREAM PROCESSES A STREAMS WANT TO BE IN EQUILIBRIUM PROFILEIBASE LEVEL AND RESPONSES TO LOWERING DOWNCUT AND RAISING SILTING B PROCESS AFFECTS STRUCTURES ESP CHANGES IN PROCESSES 1 BASE LEVEL A DROP DREDGING DOWNCUT WIDENS BRIDGES UNDERCUT 3 EROSION ON SIDESTREAMS B UP DAM BUILT SIL39l39ING UP 2 MEANDERS CHANNELIZATION SAME EFFECTS ABOVE A UPSTREAM EROSION B DOWNSTREAM DEPOSITION C ALTERNATIVE KISSIMEE RIVER IN FLORIDA D BUILDINGS IN MEANDER BENDS BAD 3 MINING A LOAD INTO STREAM SACRAMENTO RIVER GK GILBERT STREAM BECOMES BRAIDED B LOAD FROM BED SAME AS DREDGING LOWERS BASE LEVEL 1 SANDY RIVER RIVER WIDENING CAUSES EROSION C LOAD FROM FLOOD PLAIN AND TERRACE WILL BECOME BRAIDED STREAM AMITE RIVER GRAVEL MINING 1 1940 1973 1 FLOOD gt 60000 CFS 2 1973 1983 5 FLOODS gt 60000 3 1983 FLOOD 135000 CFS 4 KNOW RECURRENCE INTERVAL OF RIVER A ZONES 20 YR FP ACTIVE NO BUILDINGS 100 YR FP FLOOD PLAIN BUILDINGS ABOVE 100 YR LEVEL 8 INSURANCE 100 500 YR FP NO CHANGES B THEREFORE BUILD HOUSES USING ABOVE 5 CLEAR VEG OF STREAM GOES FASTER SO DOWNCUTS 6 IRRIGATION IF HIGH DISSOLVED SALTS FERTILITY DOWN C STRUCTURES AFFECT PROCESSES 1 URBANIZATION INCREASES FLOODING A REDUCES LAG TIME AND DECREASES RECURRENCE INTERVAL B USE PONDS TO DELAY WATER OR LEVEES 2 SEDIMENT LoADs AFFECTS DAMS A BLIILDUP IN BACK OF DAM B ERosIoN DowNsTREAM C EFFECTS LAKES FILL IN D DEPOSITS 1 FLooDPLAINs a DRAINAGE A LEVEES WELLDRAINED B BACKSWAMPS PooRLY DRAINED 2 TERRACEs GooD SOURCES OF AGGREGATE IF NoT TOO OLD TOO MUCH CEMENT IN oLD DEPOSITS ALREADY soRTED A Do NOT MINE ACTIVE FLOOD PLAIN DEPosITs 4 CoAsTAL PROCESSES A PRoCEssEs AFFECT STRUCTURES 1 sEA CLIFFs ERODE BACK MAINLY wINTER so DON39T PUT CLosE TO EDGE A IS CLIFF AC139VELY ERODING B LOOK FOR CLAY LAYERs C wATER SEWAGE wATERING LAWNS DRAIN PIPEs INCREAsE ERosIoN D WHEN LAKE LEVELS LIP OR HIGH TIDE INCREASED EROSION AND UNDERCU39ITlNG 1 LAKE MICHIGAN EROSION UP 4 MIYR FROM INCREASED LAKE LEVELS IN LATE 198039S 2 ONSHOREOFFSHORE SAND MOVEMENT IN WINTERISUMMER 1 DON39T BUILD BELOw HIGH TIDE LINE wASHINGTON ExAMPLE 3 MINING BEACH EROSION OF BEACH IIOKA BEACH JAPAN SEDIMENT SOURCE FROM CLIFF 4 TSUNAMIS RUNUP zONES FROM PAST B STRUCTLIRES AFFECT PROCESS 1 LONGSHORE CURRENT A GROINS AND DEPOSITIONIEROSION SIDES B DAMS BEACH EROSION C wILL FILL UP BAYS 2 BEACH NOURISHMENT SYSTEMS FLORIDA 1 MILLIYR 3 SEA wALLS INCREASED EROSION AND SAND INTO SYSTEM 5 GLACIAL DEPOSITS A DEPOSIT PROBLEMS 1 VARIABLE PARTICLE SIzE ESP BOULDERS 2 INCLUSIONS ESP LAKES CLAY INFILLS OF KET39LES 3 DRAINAGE MOST wELL DRAINED UNLESS LODGEMENT TILL wHICH IS HIGHLY COMPACTED B PROCESS PROBLEMS FEW TODAY 1 IF CLOSE TO GLACIER HAVE SPACE FOR ADVANCE 6 LANDSLIDE AREAS A DEPOSIT PROBLEMS 1 IF MOVED ONCE IT WILL MOVE AGAIN 2 POOR SOURCE OF AGGREGATES WEAK PARTICLES B DETERMINE PROCESS ACTIVE 1 ROCKFALL KEEP STRUCTURES amp TRAILS AWAY FROM ACTIVE AREAS LOOK AT LICHEN COVER I 2 TRANSLATIONAL SLIDES 8 SLUMPS LOOK FOR POTENTIAL FAILURE SURFACES amp IF DAYLIGHT DRAIN THEM AND INCREASE RESISTING FORCES 3 CREEP IF ACTIVE LOOK FOR PISTOL BUTT TREES AND OTHER SOIL MOVEMENT INCREASE FOUNDATION STRENGTHS AND GO DEEPER 4 ROCK AVALANCHES ZONE THE POTENTIAL AREAS AS FOREST ONLY TOUGH TO DETERMINE 5 FLOWS DO NOT ALLOW BUILDING STRUCTURES CLOSE TO STREAMS WITH DEBRIS FLOW POTENTIAL A SLOPES WITH EARTHFLOW POTENTIAL ZONE FOR NONBUILDING 7 EOLIAN SYSTEMS A HOW PROCESS AFFECTS S39l39RUCTURES 1 WHAT ARE DOMINANT wmn DIRECTIONS 3 AMOUNTS 2 WHAT ARE DOMINANT PARTICLE SIZES TRANSPORTED A LOESS OR SAND B DLINE SHAPES 8 TYPES 3 WHERE IS SEDIMENT SOURCE COVER IT IF IT IS A PROBLEM 8 WON39T AFFECT SEDIMENT TRANSPORT SYSTEM IF IT IS NEEDED PREVENT FROM COVERING WITH VEGETATION OR ARTIFICIALLY B HOW STRUCTURES AFFECT PROCESS 1 ORIENT STRUCTLIRES SO AS NOT TO COLLECT SEDIMENT 8 KARST TOPOGRAPHY LIMESTONE PARENT MATERIAL A PROCESS AFFECTS STRUCTURES 1 POTENTIAL SINKHOLES AS LOWER WATER TABLE A SO NO HEAVY LOADS B SUBSIDENCE COMMON 2 GROUNDWATER EASILY POLLUTED 3 HARDWATER FOR DRINKING B STRUCTURE AFFECTS PROCESS 1 CAN39T BUILD BIG DAMS INCREASED WEIGHT BAD AND WATER INFILTRATES INTO GROUND 9 VOLCANIC ENVIRONMENTS NEARBY A DETERMINE ACTIVITY TYPE OF POTENTIAL ERUPTION B PROCESSES AFFECT STRUCTURES 1 ASH PROBLEMS ROOFS STRONGER WATER TREATMENT AND SEWAGE TREATMENT HAVE CONTINGENCY PROGRAMS SILTING OF RIVERS 2 LAVA PROBLEMS DON39T BLIILD CLOSE TO MOUNTAIN ESPECIALLY IN DRAINAGES 3 EARTHQUAKES DESIGN FOR 5 QUAKES 4 LAHARS MAP OUT S39l39REAMS FOR HAZARDS 5 TSUNAMIS IF CLOSE TO wATER BODY C STRUCTURES AFFECT PROCESSES 1 DRILLING FOR GEOTHERMAL ENERGY MAY BE CATALYST TO ERUP39l39l0NS 1o EARTHQUAKE COUN39l39RY A PROCESSES AFFECT STRUCTURES 1 MAP FAULTS 8 DETERMINE FOR EACH A MAx CREDIBLE EARTHQUAKE B RECURRENCE INTERVAL C LAST QUAKE D g VALUES 2 EFFECTS OF EACH HAzARD ON STRUCTURE A LIQUEFACTION B GROUND AMPLIFICATION C SLIDES D TSUNAMISISEICHES FIELD DEVELOPED CROSS SECTIONS 1 AIMS AND OBJECTIVES A 13 DEVELOP PLAN VIEW OF SITE DEVELOP CROSS SECTIONAL VIEW OF SITE 2 PROCEDURE A B C D E F G H I J K 1 M N 2 FOUR A B KNOWLEDGE OF AREA WALK THE WHOLE SITE ESTABLISH SURVEY CONTROL ANY LANDMARKS OF PREVIOUS EXPLORATIONS ESTABLISH IMPORTANT ROCK SOIL WATERAND GEOMDRPHIC RELATIONSHIPS SELECT SECTIONSTRANSECTS MASURE EACH SECTION CLOTH TAPE CLINOMETER 1 SLOPE BREAKS CONTACTS SOILROCKS GEOMORPHIC FEATURES DETERMINE SEQUENCE OF ROCKS AND SOIL DETERMINE ENGINEERING CHARACTERISTICS OF EACH UNIT SOIL AND ROCKMECHANICS CALCULATE AND TABULATE SURVEYS DRAW RELATIONSHIPS IN CROSS SECTION amp PLAN CONSIDER DESIGN ALTERNATIVES CONSIDER NEED AND FEASIBILITY OF DRILLING DETERMENE FOR EACH SU SOIL UNIT AND RU ROCK UNIT c PHI AND FS APPLY ANALYSES TO USES PERSON METHOD GO UPHILL NOTE TAKER UPHILL TAPER C D DOWNHILL TAPER DOWNHILL BRUNTON COMASS PERSON 3 BRUNTON amp TAPE METHOD A B C 4 A B C D E F 5 LOOK VERTICAL DISTANCE SLOPE DISTANCE X SINE VERTICAL ANGLE INITIAL STATION ELEVATION SLOPE DISTANCE VERTICAL ANGLE HEIGHT EYES NET VERTICAL DISTANCE NET ELEVATION NET HORIZONTAL DISTANCE SECOND STATION NOTES DO OVERALL SKETCH OF SITE WITH TRANSECTS DRIVE PROBE POOR PERSON39S SPT CURVE MARK OFF PIPE INTO 6quot SEGMENTS CONNECT TWO SECTIONS PUT WEIGHT ONTO UPPER ONE AND DROP TO PUSH IN COUNT BLOWS6quot IN DRAWING CROSS SECTIONS LOOK FOR ZONES OF HIGH DENSITY HIGH BLOWS PER 6quot amp REFUSAL FOR OUTCROPS AND PUT ONTO MAP THE FIELDDEVELOPED CROSS SECTION A SYSTEMATIC METHOD OF PORTRAYING DIMENSIONAL SUBSURFACE INFORMATION AND MODELING FOR GEOTECHNICAL INTERPRETATION AND ANALYSIS Douglas A Williamson Forest Engineering Geologist Retired USDA Forest Service Eugene OR 97402 Kenneth G Neal Senior Engineering Geologist GeoEngineers Inc Redmond WA 98052 Dennis A Larson Assistant Forest Engineer USDA Forest Service Olympic National Forest Olympia WA 98507 BACKGROUND The elddeveloped crosssection also referred to in the past as the groundmeasured crosssection was developed by Douglas A Williamson during the late 1950s when the initial foundation investigation for Hills Creek Dam in western Oregon was being conducted The need for a new system of portrayal was identified by Williamson when he found that standard geologic eld methods did not lend themselves to prediction of subsurface conditions to be encountered by drilling The system was re ned during the 19605 during the Cougar Dam Oregon road location project and during the years since Williamson combined engineering survey measurement and notation methods with geologic subsurface interpretive methods to develop reliable systematic reproducible graphic and dimensional subsurface portrayals The elddeveloped crosssection is applicable to nearly all types of sitespeci c engineering geologic investigations It can be applied to excavation and placement of materials foundations and slopes mining engineering speci c development of groundwater aggregate mineral and energy resources storage and disposal sites and for accurate graphic portrayal and analysis of signi cant features related to slope stability seismicity drainage or other characteristics The basic survey and portrayal standards described in this document can be applied to any of these applications Variables include scale and minimum descriptive inventory data When various types of analytical sections are compared the applicability of each can also be evaluated A crosssection drawn from a 124000 scale topographic base map provides generalized information only because it misses even signi cant slope breaks between contour lines A section developed from a planetable map is superior because of scale but it also lacks portrayal accuracy because contour lines are interpreted elevations except at survey stations Surveyed crosssections are far superior to those taken from contour maps because breaks in slope are based on actual measurements along the bearing of the section Although they can be very accurate most surveys are either plotted in the office by computer or manually Lines between survey stations are assumed to be straight intermediate topographic breaks are ignored The computer plot is limited and actual endpoint relations may be lost Z9 S S l ial39Ig quotg 67 Sb p Appendix 35 P K39 5 A I IAp yr 139 1a J 296 Although it lacks the precision of higherorder engneering surveys the elddeveloped crosssection Figure 1 as the name suggests is a elddeveloped portrayal of actual surface relationships and interpreted subsurface relationships It is by far the most useful of all for observation and analysis of actual site conditions It is not recommended as an alternative to engineering site surveys but rather as a complement or supplement that provides rational data in an easily understandable form for decision making and design so to L0quot to L ID to so quot39 39 39 40 so so to I I I I I I I I I I I quot zzIo 1 39 295 v CRITICAL J K m 439 9 v OFFTRACKING 2890 SUA GP sandy GRAVEL brown moist compact NPL 2I 0 Origin Road Fill zno zieo 39 Finegrained dark gray 33 y 39 quot 39 uIIcs eosA 39 I sp 3939V39i amp I x I I Pn d z 4o I x j l I u 39 2130 I I I I I I 1 I I I so 20 Lou 10 Q lo 20 so MM 40 so so 10 Figure 1 Geotechnlcal crosssection 30 for the Binder Timber Sale Blair and Schelble 1983 FUNDAMENTALS OF THE FIELDDEVELOPED CROSSSECTION Elements of the Process The elddeveloped crosssection is a geotechnical team effort in applying the scienti c method to interpret and analyze site conditions for various engineering and resource applications Each fielddeveloped crosssection is a visual portrayal that provides an interpretation of sitespeci c subsurface conditions The section can be used to explain each speci c condition portrayed in terms understandable to the viewer Information portrayed can be divided into component parts to de ne the problem or condition and can be used to explain complex parts of a feature and their relationships for geotechnical modeling and analysis Portrayals are set up to facilitate organizational interaction so Appendix 35 P Z E 9 5 individuals can discuss crosssectional relationships based on their experience with the net result being a discussion based on the shared experiences within the youp As each elddeveloped crosssection is measured data are gathered independent of scale After data are reduced the section is plotted at a scale appropriate for portrayal of conditions and application to the problem identi ed This allows for considerable exibility in selecting a scale appropriate for the identi ed site conditions The system provides for continuity over time By following the system crosssectional relationship portrayals can be updated to reflect changes resulting from natural processes such as ongoing slope movement or site modi cation or development such as excavation or placement of materials in a quarry The system is designed for objectivity producing veri able and reproducible results Skills and Knowledge Required An individual measuring a elddeveloped crosssection must have a strong backgound in geologic origin and process and the ability to interpret sequence of deposition deformation and landform development The individual must be able to relate surface conditions to subsurface relationships in soil and rock He or she must have a working knowledge of the Uni ed Soil Classi cation System American Society for Testing and Materials 1987 and the Uni ed Rock Classi cation System Williamson 1987 and be able to apply these systems in the eld The individual must be able to relate physical characteristics of materials to landforms and processes and physical materials characteristics and distribution to subsurface water flow A basic knowledge of survey methods using basic tools cloth tape hand clinometer and Brunton compass is required in order to measure a elddeveloped crosssection Pro ciency at notetaking basic skills in using handheld calculators for reducing slope measurements to horizontal and vertical distances and sufficient drafting skills to plot the crosssection in the eld are also required Knowledge of design principles and construction methods is necessary to be pro cient in selecting investigative standards The individual must be capable of relating conditions and features encountered to foundations excavations slopes use of materials and permeability FESUP A working knowledge of slope stability and foundation analysis the ability to relate strengths of materials to field tests and a working knowledge of drilling and other subsurface exploration techniques used to confirm relationships and obtain test data related to soil rock and subsurface water are also required Applications of the System The elddeveloped crosssection has been successfully used on numerous US Army Corps of Engineer dam projects in Oregon In addition to dams and powerhouses the system has been applied to road cuts and lls bridges retaining structures buildings subdivisions pits and quarries waste sites drain elds sewer lines water wells water towers water transmission lines trails landings for logging slope stability analysis channel and shorelines stabilization projects sh ladders prediction of impacts from reservoir drawdown ski lifts sanitary land lls re suppression dip tanks for helicopters airport landing strips pavement design power transmission line foundations drainage Appendix 35 297 IIr1Imaarmwres structure design blast design and rock bolt design The system has been applied during all project phases from planning through construction including interpretation and documentation of asbuilt conditions 39 FieldDeveloped CrossSectionStepbyStep Procedure Serial Order of Work The following steps outline the process in serial order of completing a site investigation using the fielddeveloped crosssection investigative method 1 Develop goneral knowledge of the area This may be through examination of state maps and reports theses minerals or oilgas maps previous geotechnical investigations or explorations discussions with those familiar with the site and by developing familiarity while traveling to the site 2 Establish select survey control Survey control is expediently selected Base elevation may be estimated from map contours or from an existing site survey 3 Idontig landmarks relatoo to previous invostigatioo or exploration Data tied to these landmarks will be used as crosssectional relationships are developed 4 Examine sitesoecific relationships Landform and process are interpreted and related to the distribution of soil and rock materials and water Soil and rock units may be preliminarily established at this time 5 Select typical sections The number and locations of sections selected are tied to the types of features or processes being investigated the complexity of the site and the proposed applications of the data 6 Measure each section Sections are typically measured using cloth tape a hand clinometer and a Brunton compass Measurements include all slope breaks Pj The signi cance of each slope break that is survey station is described in the eld notebook Since slope breaks are most commonly a result of changes in materials p2 strength characteristics many times they are contacts between soilsand rock units y Measurements of contact orientation strike dip and surface trace are normally denoted where appropriate in comments for the station in the eld notebook 39 7 Determine the number ano seouenco of soil and rock units Soil and rock units are designated locally based on stratigraphic relationships and engineering strength cliaracteristics Soil units are designated Soil Unit SUA SUB SUC etc from bottom to top of the sequence Rock units are designated Rock Unit RU10 RU11 RU12 etc from bottom to top of the sequence 8 Observe gather test and document minimum engineering information for each soil and rock unit 9 Calculate and tabulate Each station established must have a survey station and elevation 10 Draw relationshios in crosssection and olan This step involves plotting survey stations drawing surficial relationships and conditions and drawing interpretations of subsurface conditions including distributions of SUs and RUs estimated locations of water original ground lines as related to existing excavated and filled landforms and slope movements and locations and continuities of quotfailure planesquot and other mass structural surfaces 11 Consider design alternotivos Relate design alternatives to site conditions relationships 12 Qoosider tl1e noed and foasibilijgy of smiling or otho soosorface eglorotion If appropriate plan and apply exploration to con rm subsurface interpretations and to gather test data Apply confirrnational information to each crosssection as needed PM 312 3 1 rf M 1 3 w 139 39 IV E K 39 quotquot quot Ar33207 3139y C 39quot39 298 Appendix 35 39 Q 1 39 9 1 39 39 39 j quot angle of internal friction C and gs or other value as appropriate Zone site on the basis of physical strength characteristics as applicable to the type of project to be analyzed to quot 39 39 39 f e is u u g al I1 o formulae blasting formulae or gthe formulae as needed 15 Apply galyses to m tended use Design a solution appropriate for the site characteristics to be encountered DETAILS OF CROSSSECTIONAL PORTRAYAL Items Portrayed The elddeveloped crosssection is designed to portray 1 topography 2 rock line 3 soil and rock units SU and RU 4 mass and other signi cant planar separations 4 subsurface waterbearing zones 5 springs should be dated and initialed and volume estimated to identify seasonal characteristics 6 surface water see item 6 7 original ground line where topography has been altered by development or construction 8 constructed features such as road shoulders base and surfacing road numbers drainage facilities ernbankments structures 9 minimum engineering information which includes descriptions and engineering classi cations of materials 10 existing survey data 11 intersections with other elddeveloped crossnsections and 12 other resource data mineral aggregate enery etc where appropriate The location measured in section must be selected so that 1 it portrays conditions typical of what it represents 2 it is normal at right angle to or parallel to the slope and 3 it extends beyond the limits of the feature portrayed and shows adjacent related characteristics The location should tie if possible to highly visible end points such as trees snags rock points orconstructed features Fielddeveloped crosssections are located in a con guration to provide all pertinent information required for the application speci ed For a slope movement feature the minimum con guration may simply be a single section following the axis of movement For a rock source the minimum con guration is two perpendicular sections that display the distribution of soil and rock units in three dimensions arid that provide dimensional relationships for crude volume calculations For ground water the simplest con guration is a crossvalley section designed to display conditions below the valley oor Figure 2 depicts the minimum con guration required for foundation investigations for various types of structures The con gurations shown provide threedirnensional portrayal under each footing For all of the applications discussed the minimum con gurations given are for relatively simple sites with few variations in slope geometry or lateral discontinuities in soil rock or drainage characteristics Additional sections both normal to and across the slope may be necessary for more complex or large sites tn adequately portray the differing conditions Roadway projects require a combination of different con gurations depending on site characteristics and design requirements The surveyed line or existing roadway in the case of a reconstruction project is subdivided into segments having similar topographic characteristics materials distribution and drainage characteristics Where slopes are smooth and uniform without complex or adverse relationships requiring dimensional portrayal typical sections are sketched Where slopes are irregular or conditions are complex typical sections are measured at right angles to the slope and if possible Appendix 35 299 OH I Qtruosacrto FIIIPEHDOGLAA M TD sternum t I r quot mmccrtn AT us ntvnrnuu Ammo couroun uun DH2 I04 39 quotwuss PLANAR 9 FEATURE P P PLAN VIEW OF HOLE LOCATIONS DHI 533quot P39i39 l390l39o3939J quot335 quot395 S nu2 9 I 5 Ft szswc DH3 l 39 P5 39 9 51 Ft Mow of soo 39 PSTA Io3a9 1 CROSS SECTION 900T Figure 8 Portrayal of drill holes on elddeveloped crosssections REFERENCES American Society of Testing and Materials 1987 Description and Identi cation of Soils VisualManual Procedure Annual Book of ASTM Standards Vol 04 08 pp 409423 39 Blair M R and Scheible A A 1983 Geotechnical Investigation for Design Road 2258000 Station 67 76 to 67 90 Binder Timber Sale Quinault Ranger District US Forest Service Olympic National Forest Geotechnical Section Ft Lewis WA 39 p 39 Williamson DA 1984 Uni ed Rock Classi cation System Bulletin of the Association of Engneering Geologists Vol 21 No 3 pp 345354 Williamson DA Neal KG and Larson DA 1981 The FieldDeveloped CrossSection A Systematic Method of Presenting Dimensional Subsurface Information abs Association of Engineering Geologists Abs with Prog 24th Annual Meeting Pg 47 39 300 Appendix 35 consistency fabric or water content Virtually every natural slope break encountered will fall into one of the categories previously listed Stations should also be established at signi cant mass planar features not affecting slope symmetry and at locations to denote signi cant features of constructed facilities Each station is marked with zi brightcolored ribbon and labeled with a waterproo ng marker indicating crosssection and traverse point number A10 for example It is preferable to start numbering at 10 or 20 to allow for later extension of the section if necessary After the survey is completed and data are reduced stations should be relabeled to indicate station designation on the traverse 1094 for example Survey Notetaking Survey notes are taken in a weatherresistant level book using the headings shown in Figure 3 which shows the standard notetaking format Using the standard format survey notes are taken independently of soil rock and water inventory data Figure 4 Minimum descriptive information for each traverse point is listed in Table 1 Measurement of the Section The azimuth of the field developed crosssection is measured with a Bmnton compass Distances and slope angles are measured using cloth tape and a hand clinometer to an accuracy of 01 feet and 05 degree respectively Measurements can be taken either of slope distance and angle or horizontal distance and rod Distances are measured at eye height eye of person running the section to his or her eye height on the eld partner when measuring slope distance and angle or from eye height to the same elevation along a level line at the station when measuring horizontal distance and rod Figure 5 The section is measured from bottom to top of slope because running the section uphill is best visually TwoPerson Method The twoperson method is preferred because it a allows for the greatest amount of ground contact and observation time per section and b allows for the greatest exibility in measurement both along and adjacent to the section In the twoperson method the person taking notes establishes the starting point if not done earlier by letter designation and number measures the orientation of the section using a Brunton compass and labels the first traverse point The person not taking notes rodman moves ahead on line to the next station Measurements are taken station to station and the team moves upslope in tandem The upslope person tags and labels stations as the downslope person gathers the geotechnical inventory data and sketches subsurface interpretations in the eld book OnePerson Method The oneperson method is used a when a second team member is not available or b when terrain characteristics make the twoperson method dif cult or impossible The oneperson method requires establishing an eye level station upslope within lineofsite distance of the bottom station This can be done by measuring to eye height on a second team member dif cult terrain circumstances in a stable stationary position far upslope on line or by establishing a station upslope at a tree or other stationary object by driving an aluminum nail at eye height and marking and attaching the end of the tape to the nail Figure 5 The person measuring the section occupies the farthest station measures its position relative to the stationary person or reference Appendix 35 301 ZOE gt 1 1 D n 5 5 UI 39spoq19u1 asoqx go uopeugqmoa 2 Sugsn pamseam sq uses zsom um suopoas xadmogt smog 1uod aouamgax am 01 azqrelax panzooy ptre paqpasap sg mgod qoea mun uopms Kq uopms adorsdn SOAOIII uaq1 pun erep Jo1usnug 12 sraqm uoums sq spqel urged 39uo1oasssom p6d08A9pp9l01EIUl0 a1ou Aemns pmpums 393 em u in grfgfggzy sr awn srveur39r nwrr lJme s4 9ccgmp pwfa B25 5606 CUPswP9 mm au mgw Fiesta sm 6 Ron HI Vb H1 3 5 1 gm 5L Eemmg 9I 8oar OF 39 41 31 5 in IE 42 f z g5n Gun 12 0 5 5 2 43 A R AM All 43 95 45 4 quot 44 99 54 3 quot7 39 f quot 745 4339 51 01 31 mg Aw 39 AIL 539 393935 47 Au M 47 3 51 3 21 vg Q A A8 3 51 4 2 394 73 at axoeas Z 2quot 51 2 420 39 25 421 1434 135 3quot 42 5 FM5AIl393smmbun L A3 A31 F 29 quot L73 I J 3 7i 7 i 49 435 amps 3 39393939lDP0FLLHL 49 I 395 quot4 F O 2494 54 396 8ea39omn 24 5 52 I Ax M cm gm 0 39 A25 3 ssmao Ban 3 235 J 0 59 2435 0 ea 54 Cwast 36 6939 39 a1 53 A37 99 4 7 3 39l3 39 C azac md LT 33 Z3 fi 3 5139 4 mm inw o I A30 5 o539 5 A31 i E1quot 5399 xnmeddv 39gtoqm sq srenbc sued sq 90 Inns aq1 rem ams39u9 01 uopoas sums aq1Jo smgod pus usemaq Bupnseam z 10 fsuopoos19n emd go smjcod a1121pam1anI1 J0 smgod pua uaazmaq Buymseam 1 Kq p9IS dI1I0313 sq 211 931301 sampm1ns reuno 01 mprurys amsop samba uopoasssoxo p9do1aA9pmay sq suomag 30 amsolg uouoesssom padoyaeppau Jo neuuo emu JBIBM pun gt100 nos pmpums p aJn6H Peosea 5w 11451076044531 sr 55 JTnr sr Jsczvoo A Loamou Psm 14397 fl rcxzAas De5C JF39Tv onl5 42 ves 5 rams m 5154a 49 153 302 Kquot I Hm 905 5 hv5 5 57 mwr HPL ma 72emf Nb Dan was DzI am commtf amp camp G Mm A13 5nnmava Aaauc Excerr four Fa86 H2 4I 3495 or 43omoeso W2ABLE SHAPED 234 mrazmz P49 5r HquotJ Acwn5 Va rminI Read 5u57 2299 iLaAc punL6 EYC 119 73PvFaauw6a couvncr mnab A0 V RJ7cfA meat AMr u5 Aw R czf s f Jo 40 7AJ5J kb 357 Fus 19 Z Momp J suemrr 76 3 bat M50 Igt24 re A451 cauorsrald B2ouw coma GM m1 oensu3 abac sr nu 433 3499 um939 Rm snaps 9uTT 5 0 OLD Mazrnaeo aay ger9 J5 twm 4z23942e39 sre2e4 o zgt caucema Fbmz 47oA5 Butts Came 394 339 Fwwmmb 434 5 e54y Ow 8cm 5 A35 395E5C4SgtquotF7u 6394 73 A7 A24 Qwa dear9 z mIJ up 85er1 470 ydsmmr 7m4au 430 43 43157 wo Jarat xii 433 30 CU739Lgp 345417quot C312 39 u awn Ci5 BeauU awe ezmaugspp E Fm 5 ar s 4oz LmJ same ampLamp 4393 9 fe 22 uo 22 uggs E mesa E 29 qr3 CEEEC 433 CoaumcrHaezoum R 93006 l539A54u3939CoO we6usjgt 3 Swen 7quot1 BArrgt PG 239u39 Rear 8LocIC619 B quotquotJf 3973UB D 39 A quotquotW 3557 ZOE I709 FELDIBJTFKJATIJIPBOCEIES xdudng parade Iarmr thana In and bulngfrusclens on oslrmund heights GFIAVELS um or UNIFIED SOIL CLASSIFICATION INCLUDING IDENTIFICATION AND DESCRIPTION I3939FIOUFquot SYMBOLS TYPDAL NAMES MINIMU M INFO FIMATION CH ECKLISTS HcxK wmsn 9 1 Ram puma rennet 1 Coco 57 239 cob LATENT oven on cmseo 2 Volume How Chnrncbrlsdcn 239 cob 3 Dogs dwaatharlng Oriya frnlnanai win etc 05 quot 5 ODPGNNII 3 M I39 quotquotwquotquot 39 n39m9 i quotamquot 4 Brain Slza Strength oflllng lcornpanwith host rock I1uldmou d Opening 4 OHSquot 5 39 quotquotquotquot39 5 Irnpaci udnau mow auction to hmmoruou Ibnakaan Parana Maud Angles 5 Tornparnlura 39 quot g mum sggm ons Angdar Fhh one pi Pnrllld Filld Angus C7l39l not 0 Turbldty Fquotquot Thldmon cl Planar Feature Shnot Formed 7 WPquot 39 5quot F quot quot quotquot quotquotquot F quotquotquot39 739 awwm Pamliul rchbd undo sum Hulls a own 1 5399PQndad Mamhlc quotquot cc 3 Ralathu Abeorp on rahbd undo a nou Introduced Finn use rnln sci duetr cum 9 Mode at meananon E gin 10 Inchxcmracbds cs Shapes Formtd Minn Tranamlulon tvalurnan fromftul 10 Exit 1 11 Mamnntuda sudnco ald Drb h b i mddpl 339 u quotquot39 gquotquot39 12 origin onormon sun and dp a Dry anngm 9399 xmuaddv SW3LSAS NOILVOIIISSV39IO quotHOS ONV IOOII CI3IINI39I NOILVOI39IdclV CINV NOLVOIILNEICII CI39I3II 39 I339IBVL ROCK MASS STRENGTH ESTIMATES BASIC ELEMENTS EFFECT or WEATHEFIING WEATHERquot so ALTERED FIEPRESENTATNE 39 quot39 smo SIZE GFIAVEL SIZE smusn STATE VISUALLY M1685 nEsHquotquot COMPLETELY PAHTLY srsi sass4 STATE oecoupossn oecouposan STATE HAND LEN5 STATE cos STATE PBS 9Fs ups E D C B A PLAS NONP Puusnc NONPLAS c39o M39P39 Aa e T0 ER 5574 s39T39ATs Fnquot we tomquot 39a39E1ATwE ABSORPTION MINERAL GRAIN BONDING 39 quot 39n eMou3No FrAc noN T0 IMPACT MOLDAB c 39nATaas oeNrs Prrs aeaouNos FFHABLE snares ceoupnesswa 39lENSl0NAL aAsTrc M31I C0 030 P0 RD E D C B A lt 1000 PS 1000 To soon 53 3000 To aooo PSI sooo To 15000 PSI a15000 Pquots 39 3 MPa 7 To 21 Man 21 TO 55 MPaL yss To 103 Mm gt103 MPuL PLANAH AND LINEAR ELEMENTs 39 mmsmrrs wmsn 39 quot vssquot39 No Yes No 3 DIMENSIONAL 2 osNsoNA1 LATENT souou soun PLME8 or PLANES ou PLANES or PREFERRED rwaoou SEPARATION SEPARATION SEPARATION anemxcas anaamee 39 20 193 SP3 333 E D C B A uNTEruocnlt ATTITUDE UNIT wencwr LESS THAN 130 To 140 140 T0 150 150 T0 160 GREATER THAN 130 uasicu FT LBSJCU FT uasrcu rT Lasrcu I T 1so LBSICU FT 210 Mg PER cu M 210 To 225 225 To 240 240 T0 255 255 Mg PER cu M lt13o Mg PER cu M Mg PER cu M Mg pen cu M 130 140 150 gt160 E D C B A UNIHED SOlL CLASSIFICATION AFTER AMENCAN SOCIETY FOR TESTING AND MATERIALS 1987 UNIHED ROCK CLASSIFICATION AFTER WILLIAMSON 1984 I The purpose of closure is to give the engineering geologist measuring the section a means of checking his or her work to ensure that all points have been measured within a reasonable range of accuracy While not intended to represent a legal survey a lack of careful measurement can rnislocate a key reference point for foundation location or not provide a proper topographic pro le for slope stability analysis Error in closure should not generally exceed 1 foot per 100 feet of line Closure error should be noted on the rough draft section and adjustments made during preparation of final drawings Data Reduction Data can be reduced either in the eld notebook best for eld reduction Figure 6a or on a separate piece of paper most accurate method if reduction is done in of ce or if section is to be plotted by someone other than the person who measured it Figure 6b Data reduction is accomplished by using a handheld calculator to compute vertical and horizontal distances from slope distance and vertical angle in degrees This can be done by converting from polar to xy coordinates or by using trigonometric functions Appendix 35 305 306 v 9r I ksF39 a Flguro 5 MEASUREMENT OF SLOPE DISTANCE 4 TAP cmtmm Aum rmrzoum um POINTS If NHL ILEVATIGI M 39Asm 39HEJvr aF mzmvr D l539739ANCE39 I WHEN RUMVIN6 LEVELS TIE TIIPE OFFATEYE HEIGHT USE TREE STAKE RG7 OR WHATEVER IS AVAILABLE ALUIIIIUI HAIL IIITII IIIIBN A I lllill 39 i39i3923 Measunlng dlsmnces between traverse polrits Appendix 35 539 xwuaddv sq sun5 2 SE qons any Kauns B sassom uoyoas sq 919 39tnessaaatx amp 1911212 19 uogsuazxa mom 01 0001 qum 511313 Anansn 3IImo139e1s aqL paqs39g q1z1sa em s39uo1tzAaa wooqezou men an U sexou Pl9B peonpea 3999 esn ls oszomn rpm 10 trguopmg 39pos11 5 uyuopms 339I1S 39X9 aq1 augpmuao a ppq 912 qans Kazuns Bupsgxa I112 smono uoppos sq amqm passer uopms sq 01 paouaxagaz 9 uopoas pue suoyrezs Iraq snugod 2 Jo po1ungt139eo am sootrmsgp reopxaa pure re1uozuoq aouo Peoaecr Su m urea 39 s mm A Lac P m gjzgf SW6 zrmeum xuvrsr ug wagi 43349 3 Faom Sm 55 R9115 H mm Hg 3g 12 gm EL Rm eu Au mquot 4395 am An mH 45943 3 51 31 8 m2mm1 4qz Ennfoc NZ 7 44139 07 57 5 339 21 Ar5ow4a1 ma quot 3mT Ali 5 I A13 mes 7 1 2 4 9 Aw am H 1 1 Hi A 439 3 quotquot 5 Fw39ltquot e 9 49 quot 9 54 AI5so634 sax p o scans 39 quotquot I 8 Ins AIS39oa5L4 a39 43 57 5 33 ALmH24u9 I6 Am A1910F39 4H3 29 45 539 45 7 E Q as Ame7 4943 23 51 31 239 5 542 4 B Z 1 0 I 139a 2 52 22 hY m m 7 5 5 2 39A2NgtIA 413 unsure cusses can Am quotFquot 475 5quot 39339 I31 I25 A22 In55393941s9 A21 39 quot 417 Hg 51 Azzu ssquot 4135 355 V A26 2 E J W Io5 wag 5 1 5 5337 46 A abreo A353 T mks 3512 7h d4uI4u 2539 2zs a Am mm as 11 539 52 A25m554n9 4 m A25 I0433 39499 62 52 03 59 49L lug us 4991 2 1 0 53 35 P 6 0senusaaoeamas 39 L 1 Q 2 soab 4 db A28 39 3 439quot 5 5 0 16quot A29 toms 4193 gm us As 3 429wot m 49 52 1 23 Am aoa31rquot Q3265 Aaomro quot473559 52 01 1 A3Ioyoa49BEfI39IH M21 A L09 Pltt IJEc39139 111 rmv 6391 551 1Amlnarmn mur SECTION A REEF392OI39iiH 11913 ITIquot1quotIAI3 DESIGNATION STATION EIEVATTUN i Am o67 473 2 2 AIG os93 41103 4L 2 amp I8 IOl75 468339 z 55 A n Io39 4 44 9 4 29 mt o391 339 419 51 40 A15 Itgt485quot am 1 4 5 5 44 o438 quot 45 394 AI3 1o9539 4139lquotquotquot U 23 59 X 1392 IIo75 H239 V ll 5 23 V Z F AH IHl9quot39 l293 S Figure 6b Reduced field notes on separate reduction form point is then calculated based on horizontal distance from 1000 Stations are assigned such that station numbers increase from left to right as viewed looking ahead on line along the referenced survey if one has been established Elevations are calculated and listed for each station on a reduction sheet or in the eld notebook quot 308 Appendix 35 TABLE 2 APPLICATION OF VARIOUS CROSSSECTION SCALES Selection of Scale Table 2 shows the range of scales generally appropriate for various fielddeveloped cross section applications All sections in a report should be portrayed at the same scale if possible for ease of understanding and application Section Layout The fielddeveloped crosssection may be plotted on a variety of materials For eld plotting particularly in areas where conditions are commonly wet layout on frosted mylar has been the most successful Commercially prepared sheets 812quot X 11quot 1139 x 17quot or 223939 X 36quot with a 01quot and 1quot engineering grid are commonly used for field plotting Layout is completed by rst establishing horizontal and vertical reference elevations and stations at the selected scale plotted top and bottom and both sides Stations are plotted from left to right unless there is a special need such as to have fielddeveloped cross section stationing easily discernible from a yet unestablished site survey For Appendix 35 SCALE quotquot39I397PE or mvenronv ANKrv 1I39 neponr PROJECT METRIC ENGLISH METRIC N ENGLISH SLOPE 1100 1120 1100 1120 1100 1120 STABILITY 1 cm 1 m 1 In1011 1 em 1 m 1 In 1011 1 cm 1 1 rn 1 In 1011 to to 10 10 to 1300 1300 1600 1600 11000 1 1200 1 cm 3 m 1 in 1 2511 1 em 6 m 1 In 5011 1 em 10 m 1 in 10011 STRUCTURAL 1100 1120 1100 1120 1100 1120 FOUNDATION 1 cm 1 m 1 In 1 1011 1 cm 1 m 1 In I 1011 1 cm 1 m 1 In 10 11 CUTSLOPE 1100 1120 1100 1120 1100 1120 EXCAVATION 1 cm 1 rn 1 ln 1011 1 cm 1 m 1 In 1011 1 em 1 m 1 In 1011 ROAD 150 160 150 160 150 160 BASE AND 1 em 05 m 1 In as 511 1 em 05 m 1 in 511 1 cm 1 05 m 1 in 5 11 SURFACING to to to to to to 1100 1120 1100 1120 1100 1120 1 em 1 m 1 In an 1011 1 cm as 1 In 1 in 1011 1 em 1 m 1ln1011 EMBANKMENTS 1100 1120 1100 1120 1100 1120 1 cm a 1 rn 1 In 2 1011 1 em 1 m 1 In 1011 1 cm 1 m 1 in 1011 DRAINAGE 1100 1120 1100 1120 1100 1120 1 em 1 m 1 In 1011 1 em 1 rn 1 In 1011 1 em 1 m 1 In 1011 to 10 11000 11200 1 em 10 m 1 In 10011 ROCKAND 1100 1120 1100 1120 1100 1120 AGGREGATE 1 em 1 m 1 in 1011 1 em 1 m 1 In 1011 1 em 1 m 1 In 1011 SOURCES to 10 10 lo 10 10 1600 1600 1600 1600 1600 1600 1 em 6 m 1 In 50 11 1 em 6 m 1 in 5011 1 em 6 m 1 in 50 11 309 crosssections too long to plot on one sheet end points of sections and drawing reference points are matched carefully for taping Each facet must be labeled carefully to ensure a later match for final drafting Each elddeveloped crosssection must have a bar scale The title block for each section is located in the lower right hand corner for uniform referencing The title block must include project location and type of survey used Bearings and bends in the section are shown along the top of the page Figure 7 Portrayal of Subsurface Conditions The portrayal of subsurface conditions is the most critical aspect of this method because 1 it is the primary reason for measuring the section and 2 it is the major element that distinguishes the fielddeveloped crosssection from all other techniques The portrayal of subsurface conditions requires a correct geological site interpretation geomorphology stratigraphy and structure to be accurate The rock line is the top of recognizable rock in place observed as a rock unit Rock in this context may range from completely decomposed to solid The rock line is portrayed based on rock exposures and projection of rock surfaces and the interpretation of sur cial features and materials strengths and weaknesses Rock and soil units are shown by sur cial relationships along the section and by projection from adjacent outcrops Contacts between soil and rock units and mass and other signi cant planar separations are drawn to portray their apparent dip in the plane of the section When intersecting sections are drawn the same plane must be portrayed at the same elevation at the intersection on both sections Drilling may be completed at a later date to confirm subsurface interpretations Drill hole location requires remeasurement from an established station on the section When drilled on the section drill holes are drawn to scale on the section including any surface modification for drill set up and operation Holes drilled away from the section may be portrayed in one of three manners depending on the objective of the portrayal Figure 8 The most common method of portrayal is to project the hole into the plane of the section at right angles to the section Hole locations are designated as ft right or left of section DH1 in Figure 8 Alternative and less common methods include 1 projecting to the section at the same elevation as the top of the hole hole locations are designated as ft at bearing from the station shown DH2 in Figure 8 and 2 projecting along strike of bedrock to the intersecting point on the section hole locations are designated the same as above DH3 in Figure 8 In all instances drill holes are drawn to portray true top of hole elevation that is the top of hole may lie above or below the elevation of the corresponding point on the section ANALYSIS AND APPLICATION Analysis of data gathered during measurement and con rmation of fielddeveloped crosssections for various purposes includes the following steps and phases 1 Data Reduction During this phase raw eld descriptions and classi cations and laboratory and drill test data are evaluated and sorted to determine pertinence and 310 Appendix 35 applicability to the problem or need Extraneous data are discarded Information to be applied is re ned from description and classi cation into numerical values such as bearing capacity uncon ned compressive strength cohesion angle of internal friction mass or weight con nement permeability porosity rate of weathering rate of water transmittal or other more specialized values 2 Zgnatigng Strength or other values pertaining to the problem to be solved are displayed on an analysis copy of the elddeveloped crosssection Differences and similarities in values are noted Boundaries reflecting changes in value are drawn A zone diagram is superimposed or overlaid on the elddeveloped crosssection Figure 39 7 reflecting topographic characteristics zone boundaries and pertinent numerical values The zone diagram is applied to design and contract applications A copy of the analysis section is kept for reference 3 Desig Analysis of Altematives Alternative lines and grades are plotted on copies of the zone diagram Design suitability and limitations construction problems probable impacts from construction and material needs are estimated either by judgment or through use of a mathematical model if a suitable model is available or can be developed SUMMARY AND CONCLUSION The elddeveloped crosssection method was originally developed to provide a systematic and reproducible method of collecting data for portrayal of subsurface conditions expected to be encountered during drilling It has evolved into a system that hasxsigni cantly improved the ef ciency and reliability of the investigative process for 32 to date different kinds of engineering geologic project applications The elddeveloped crosssection investigative method requires systematic measurement observation testing classi cation and recording of data at each station Hence the process yields reproducible results largely independent of the personal skills and knowledge extending beyond required basic eld tests plus skills in descriptive geometry and geomorphic and structural interpretation A journeyman engineering geologist can with a minor investment in training direct eld crews of less experienced geologists to obtain very reliable and accurate eld data and then can apply his or her experience and knowledge to analysis and application of that data Thus the system allows the journeyman engineering geologst to extend his or her skills through utilization of others When conditions portrayed are tied together and projected in plan as well as section threedimensional relationships are readily visible for the type of analysis needed Potential alternatives can be applied visually and dimensionally directly to the elddeveloped crosssections Often visual observation of relationships applied to the alternative will yield answers directly without necessarily requiring the application of statistical or other mathematical analysis methods If mathematical analysis is required the fielddeveloped crosssection provides a reliable model Since selection of stations is related to real ground conditions the data once tabulated is independent of scale The scale selected for the section is one that best portrays the conditions investigated The portrayal of conditions allows the resulting fielddeveloped crosssection and zone diagrams to be used as a medium of communication This system readily bridges the barriers of discipline and scienti c nomenclature Appendix 35 311 9400 9490 IOIO0 IOHO lO2390 IO3 IOI40 I0Igt I I I I I I I I uumv o zone In 14 TSF 850 unauuruauu 139 Ia Nn quot 39nn39 39 zone IV 576 TSF 520 111Ia Orayinll undt w 6lO soo 490 459 410 400 450 39 uumcn noel cLAssIFIcA139Iou SYSTEM Cl ervllllhrluon 1970 I I I I I I I I oao 0W I01O0 I0l0 IOI20 I0I30 IOI40 I0If0 V Figure 7 Flelddeveloped crosssection and foundation zone diagram 312 Appendix 35 4 IoIso IoITo Ioao IOO90 IIIoo llHO I I I I I I Ltorna UIFICO Ell QJIIIFICATIX IYITCI an quot quot39 It ran Em on raw 39 397 cc rcu 2133 ccrc 39 III M 3quot 1 ran an run xrcu I lil xmr W H I ct we Zone I V Unsafe Con nement arm avcu AuIII auriminq 01139 DODHI Guunh o IDQIIIIgI39IIIII T0MlIl398aIIaroFol 9 D ID 4 Nil II FIIT m quot 5 39 5sx I I 3939 lt 3939 I aw uourooutlw when an 139 39 II g I39 I 31 339 FouunAnaII Ann I SLOPE STABILITY INVESTIGATION I 39 AIIoIounII3IvII39IoII zoraouawu FIELD DEVELOPED cnosssIcTIoII 1H 1t snraou n5 I l I I 39hquot39 739a39quotIr39Ila39 13iv 39 Io39Io Ioeo Iooo IIoo IIIo FIGUHE7 1 I0I60 Figure 7 Continued Appendix 35 313 r 39 39 nuruturq 39 quotcm 19 1 1 or ntrmmua mu Irolndurlou menu cum quotquot quotquot quotquotquotquot eeroun onnames mun Ir meucrune BRIDGE FOUNDATION L cursLoa a 39 tL m I ureter can DOINSLDPE um 1 r139 J mono nmusunon rm I muter I I I I mrrammva nmu FOUIVDA now I I I I I I mi 1 I J I I I I 39 39 39 I I I I L l I L 393939T I BUII DING F OUND4 TIOIV 5 Figure 2 Minimum fielddeveloped crosssection configuration for various types of foundation Investigations perpendicular to the survey line Each section must extend beyond the feature requiring portrayal at least 100 feet either side of the surveyed line or to a ridge top or valley bottom if closer than 100 feet The section must show the range of conditions typical for that segment For road segments involving stream crossings where special structures may be designed or where the alignment crosses a slope stability feature the elddeveloped cross con guration for that speci c type of investigation is used Selection of Stations Once end points of the fielddeveloped crosssection are selected and marked stations to be surveyed can be established Stations can be selected either before or while measuring the section The line should be brushed if necessary before selecting stations NOTE Be sure the landowner gives permission to brush Points selected for survey stations are usually slope breaks because slope breaks indicate a change in materials strength characteristics such as in rock a change in texture hardness fabric weathering or structure or in soil 3 change in texture plasticity compactness or 39I 3 5 P 4 rs 314 Appendix 35 G47 0570 REGULATIONS AND BUILDING CODES 1 Chapter 16 UBC Quality amp Design of materials used in construction A Design of structures depends on seismic zones amp site geology also height occupancy con guration B Seismic zones Zone 4 for south coast zone 3 for north coast and up to crest of Cascades C Site coef cient for soil S factor Table 42 D Period of soils and peak ground acceleration Fig 41 1 Used to calculate lateral forces for a building V CW E Accelerographs 3 required in most buildings over 6 stories high 2 Chapter 18 Excavation and lls for structure foundations and retaining structures A Expansive soils if expansion index gt 20 it requires special design B liquefaction test required for sandy soils with high groundwater table C written reports usually contain plot map of borings and excavations soil classi cations elevation of groundwater table recommendations for foundation type bearing capacity mitigation of liquefaction expansive soils and soil strength and expected soil settlement all of above during earthquake too use peak ground acceleration that has a 10 probability of being exceeded in 50 years D See Table 45 max foundation and lateral bearing pressures for diff materials not to be exceeded E Building and footing setbacks for 31 slopes 1 at bottom of slope H2 but not gt 15 2 at top of slope H3 but not gt 40 F Possibility of groundwater table rising above oor level 1 if GWT close to surface need drain system called dampproo ng 2 if GWT exerts hydrostatic pressure on structure need waterproo ng 3Chapter 31 ood resistant construction AFlood hazard zone A wave heights lt 3 1 lowest oor above 100 year ood elevation 2 can have storageaccess amp parking below 3 drains must be watertight walls must support building during ood B Flood hazard zone V wave heights gt 3 1 lowest oor aboe 100 year ood elevation 2 must be on piles amp free of obstruction 4Chapter 33 Excavation and lls grading permits Aif make excavation gt 12 deep must protect next property amp give 10 days notice B must remove stumps and roots in top 12 of soil C Types of Grading 1 Engineered Grading gt 5000 cubic yards needs soils report engineering geologist report if geological hazard lt 5000 yds can be classi ed as engineered grading 2 Regular Grading lt 5000 cubic yards plan includes only dimensions of cut and ll and location of buildings D Cuts no steeper than 21 only ok is reports can support it E Fills 1 not constructed on natural slopes gt 21 2 remove vegetation amp topsoil of slope for bond 3 where slope gt 51 benches cut into slope 4 bench under toe gt 10 wide 5 no organic material permitted in ll 6 no rocks gt 12 in ll if there must be gt10 below grade 7 must be compacted minimum of 90 max density when compacted 8 ll slope cannot be steeper than 21 F Setbacks 1 top of slope 115 2 min and 10 max 2 bottom of slope H2 2 min amp 20 max GDrainage and Terracing if slope gt 31 1Need terrace at least 6 wide at 30 intervals to control surface drainage and debris 2Subsurface drainage may be needed 3Erosion control by downdrains and paved interceptor drains at top of slope plantings HMust have asbuilt reports civil engineer soil engineer and engineering geologist IWhen liquefaction report needed 1Seismic Zone 3 or 4 2unconsolidated sandy alluvium 3shallow groundwater 50 or less 418 LEGAL REGULATORY 1994 UNIFORM BUILDING CODE APPENDIX CHAPTER 33 continued SETBACKS Sec 3314 continued Top of Permit Area Slope Boundary H5 but 2 ft min and 10 ft max Permquot Area 2 1 39Si 39Gde Boundary Toe of I ope Slope H H2 but 2 ft min and 20 ft max Natural or Finish Grade Figure 43 Slope Setback Requirements From Site Boundaries TND AINTAFIE ATTT TEDD AF IITF Q39Jr quotl39I1 2 Where a retaining wall 1S constructed at me LUC U1 L11L slope LLLI g measured from the top of the wall to the top of the slope 3 Figure 4 2 UBC Figure 18I39 1 shows the setback distances for footings from the top and toe of the slope Alternate setbacks may be approved by the building official or the building official may require an investigation and recommendation by a registered engineer 1 Footings on or adjacent to descending slopes must be founded in firm material with an embedment and be set back far enough from the slope to provide support without detrimental settlement Protection is assumed to be provided by applying the following criteria 1 Where the slope is steeper than 1H1V the required setback shall be measured from an imaginary plane 45 to the horizontal projected upward from the toe of the slope 2 Setbacks shown in Figure 42 UBC Figure 1811 must be met unless a building official approves alternate setbacks An investigation and recommendation by a registered engineer may be required Face of structure H3 but need not Toe of exceed 40 max V Slope A H2 but need not exceed 15 max I Wquotquot a Top of m Slope T H Figure 42 Footing Setbacks From Slopes the seismic zone ractor A Provisions shall be made for the control and drainage of surface water around buildings see also Sec 18064 ALLOWABLE FOUNDATION AND LATERAL PRESSURES Sec 1805 Table 18I A of the UBC modified and presented here as Table 45 provides values of allowable foundation and lateral pressures for different types of materials Values in the table are maximum values and are not to be exceeded unless data are submitted to substantiate higher numbers UBC Table 18IA may be used for structures not greater than 3 stories high having certain foundations on rock or nonexpansive soil or for structures having certain types of footings TABLE 45 MAXIMUM FOUNDATION AND LATERAL BEARING PRESSURES UBC TABLE 18IA MATERIAL FOUNDATION LATERAL BEARING PSFFT PRESSURE OF DEPTH BELOW PSF NATURAL GRADE Massive crystalline bedrock 4000 I200 Sedimentary and foliated rock 2000 400 Sandy gravel andor gravel GW and GP 2000 200 Sand silty sand clayey sand silty gravel and 1500 150 clayey gravel SW SP SM SC GM and GC Clay sandy clay silty clay and clayey silt CL 1000 100 ML MH and CH Organic clays and peats OL OH and PT Foundation investigation required 1995 by Osiecki 8 Dirth DYNAMIC LATERAL FORCE PROCEDURES Sec 1629 Buildings subject to dynamic analysis procedures must have a ground motion representation that at a minimum has a 10 probability of being exceeded in 50 years Acceptable representations include 1 A normalized response spectrum provided in UBC Figure 163 and redrawn in Figure 41 2 A sitespeci c response spectrum based on geologic tectonic seismologic and soil characteristics at the site Ground motion time histories representative of actual earthquake shaking at the site 4 For structures on Soil Pro le Type S the representation of ground motion must be developed using items 2 and 3 above and must include a consideration of soilstructure interaction that may lead to amplification of the building response and inelastic behavior of the building leading to a lengthening of the building period 5 Scale the horizontal accelerations by 23 to obtain the vertical acceleration DJ 00 I L i I H Soft to Mediurri Clays and Sands Soil Type 3 Q Deep Cohesionless or Stiff Clay Soils Soil Type 2 I i 1 lD PEAK GROUND ACCELERATION 1 Rock and Stiff Soils Soil Type H O i i 5 4 0 5 0 05 10 15 20 25 30 PERIODT seconds Einnro 1 1 DIquotY f39Y lquotquotJ39Drquotl D39mcnrnm gt Qnicr trin Fnr Tlwrpp Qnil Txrnpc 1116 Uttblb LUL upmbu I1 characteristics occupancy factor configuration structural system planned and height 1 ll ggs provides input on the seismic zonation and site geology and characteristics while the structural engineer is concerned with the other design items All of California is within Seismic Zones 3 and 4 as shown in UBC Figure 162 Zone 4 is the highest hazard zone recognized Each structure is assigned a zone factor Z based on the seismic zone in accordance with UBC Table 161 Zone 3 has a Z of 03 Zone 4 has a Z of 04 The characteristics of the ground at the site are categorized into 4 types as shown in UBC Table 16 and summarized in Table 4 2 The site coefficient S is obtained from geotechnical investigations If the soil conditions cannot be determined in enough detail to categorize them soil profile S3 is used as the baseline TABLE 42 GROUND CONDITIONS AND CORRESPONDING SITE COEFFICIENT SOIL PROFILE TYPE GROUND DESCRIPTION S FACTOR S 1 Rocks with shear wave velocities gt 2500 ftsec or 10 2 Mediumstiff to stiff or mediumdense to dense soils with soil depth lt 200 ft S2 Predominantly mediumdense to dense or mediumstiff 12 to stiff soils with soil depth gt 200 ft 83 Soil pro le with gt 20 ft of soft to mediumstiff clay but 15 i not more than 40 ft of soft clay 8 Soil pro le with gt 40 feet of soft clay having a shear 20 H wave velocity lt 500 ftsec Five occupancy categories have been established for all structures as shown in UBC Table 16K Category 1 is for essential facilities such as hospitals and emergency response services and Category 2 is for hazardous facilities Category 3 encompasses special occupancy structures where large groups of people may congregate Category 4 covers standard occupancy structures and Group U occupancy towers and Category 5 is a new category covering miscellaneous structures Each occupancy category is assigned a seismic importance factor I for earthquakes The seismic importance factor for Categories 1 and 2 is 125 while the seismic importance factor for the other three categories is 10 LECTURE ON GRADING AND EXCAVATION 1 Appendix Chapt i own as th in Los A code rst 1952 Angeles adopted the first grading code rst adopted in Oregon in 1998 A Re a PA geotechnical engineer and 3939 ngine ogist B geology geohazardss slope bility C Cuts no steeper than 50 slope unless report contains overwhelming evidence of stability D Fills not to be constructed on slopes gt 50 1 must prepare slope remove vegetation noncomplying ll topsoil so fll can bind 2 if gt 20 and gt 5 ft height must have bench under toe into sound bedrock or other competent material that is gt10 ft wide E 0 material types compaction rainage and collection erosion control 1 2 3 4 5 6 7 3 9 INGREDIENTS FOR GOOD LEADERSHIP Have a vision dream goal Passion for your role enthusiastic be a motivator Integrity a Know yourself strengths and weaknesses b Set an example walk what you talk Maturity be broad based lots of experience continually learn Good listener Honesty develop trust from others sensitivity CuriosityDaring turn failures to successes willing to take risks Communication skills written and oral Technical competence 10 Organized 1 1 Give thanks to others 12 Delegate responsibility to others surround with leaders team decentralized decision making 13 Time management time for re ection and strategic planning time to play time to invent 14 Sense of humor 15 Openminded listen to all sides 16 Servant leadership will to volunteer and serve others 17 Dress like a leader EXERCISE 2 MOHR CIRCLE OF STRESS I n their natural settings soils and rocks are subjected to forces from such things as overburden and structural deformation Construction typically alters the forces in a soil or rock mass Forces can be compressional as in the case of overburden loading tensional as in the case of unloading of natural forces during tunnel construction or shear as in the case of failure along a fault surface In practice force is converted to the unit measure stress to provide a measure of force per unit area Stress is measured in lbsin2 psi in English units and Nmg Pascals or Pa in Standard International SI units Stress is a vector quargty becauseitis a measure of directed force Stresses may be compressive tc3nsilemosr shear all iilirectionalquot in space The Mohr ci s or M0hr s circle is a useful graphical represen tationo39f quotjthe state cg stress at a given point within a body The generic term body is used here to represent a mass of unde ned material Mo r s circ e an be used to analyze stress amounts and directions acting in a soil or rock mass In practice it provides unique strength limits for a material subjected to compressive or tensile stress under given loading or unloading conditions Exercise 3 expands on this using test data and analysis of results from a practical viewpoint Before the construction of a Mohr circle of stress is described the various stresses acting on a unit mass within a body must be understood We will consider the stresses resulting from the application of compressive stress in just the XY plane of an elemental cube unit mass A useful starting point is that of an equilibrium stress eld for this twodimensional or plane state of stress example Figure 21 In this figure conjpressive and shear stresses are noted respectively by the Greek letters a a h compressive stress acting normal to a surface creates a shear stress perpendicular to it In the equilibrium state shown the shear stress moments in the X and Y directions are zero The compressive stress subscripts shown in Figure 21 indicate the axis along which the stress is applied normal to the element By convention in engineering applications the positive stress directions are compressional The dual Txy subscripts for shear stresses indicate the shearing K tendency relative to an axis and the direction of L shearingThus the shear stress 7 denotes shearing i normal to the Y axis and along the X axis with the arrow showing the direction of shearing Figure 21 EXERCISE 2 Mohr Circle of Stress 9 We can model an example which will be useful in Exercise 3 In Figure 22 an inclined surface has been constructed which intersects the Y axis at an angle 6 Think of this as a surface along which shearing may quotgtltgt occur as shown by the shear stress 7 and the K compressive stress 0 acting normal to this surface and 0 N at an angle 6 to the X axis This normal stress 0 can be Tm resolved into two orthogonal compressive stresses 0 and 0 which are parallel to the X and Y axes respectively 2 T Associated shear stresses 7 and r are shown on the gure 0 Although not obvious at this point in this exercise there Figure 2 39 2 will be a unique value for the angle 6 where the shear stresses 7 and 7 will vanish For this value the X and Y axes are called the prirtcipal axes of stress and the stresses 0 and 0 become 0 and 02 the principal stresses for the two dimensional case being used in this example Mohr circle construction utilizes two orthogonal axes 0 and T as shown in Figure 23 The 0 axis is known as the normal stress axis and all compressive and tensile stresses are plotted on it In our case only compressive stresses will be used and these are plotted on the positive or right side of the origin Shear stresses are plotted relative to the 739 or shear stress axis with positive values being above the 0 axis Figure 23 shows compressive and shear stresses acting on some plane other than that de ned by the principal axes 01 and 02 Thus it graphically shows the stress conditions generated by stresses 0 and 7 in Figure 22 4 M Plotting of the points 0 7 and 0 r as shown in the Tyx 4 p59 TF0 gure results in two points on the Mohr circle The W a I 0 complete circle is the locus of points for all values of 26 2g 7 n2 P 2 The center of the circle can be obtained graphically from 0 quotii 9 the intersection of the line joining the two points with the 0 0 1 T 0 axis By convention rotation of the plotting of 0 7 and 0 7 values is clockwise about the center of the Figure 2 3 circle Thus the 0 7 point is plotted below the 0 axis relative to the center of the Mohr circle and the 0 7 point is plotted above the axis The signs of 7 and 7 indicate their relations to the 7 axis The angle 6 de ned by Figure 22 is shown in Figure 23 It can be calculated or obtained by measurement of 26 by protractor from the Mohr circle construction In Figures 22 and 23 it can be seen that as 6 approaches zero the normal stress 0 also approaches zero and the shear stresses will approach zero This results in the X and Y axes of Figure 22 becoming the principal axes as stated above The 0 axis of Figure 23 is the limiting case where at 00 and 60 001 and 002 thereby becoming the principal stresses for this planar model The graphical representation of the stresses shown in Figure 22 is easier to grasp with the Mohr circle shown in Figure 23 In addition use of the Mohr circle permits one to evaluate stresses in a variety of orientatio13squot tfthe principal stresses as in approximating eld or experimental conditions and determining stessfconditions at failure in laboratory testing aanquotW 10 Engineering Geology a Laboratory Manual In practice stresses will be acting along three principal stresses 0 02 and 03 where 0 is the l maximum stress or stress at material failure 02 the intermediate stress and 03 the least stress 39 When a material is con ned either in nature or the laboratory the con ning stresses are T2 and 03 These stresses are usually considered to be equal for ease in testing even though this is not the case in nature Although the Mohr circle provides a graphical solution for the stresses shown in Figures 22 and 23 it is useful to calculate 0 02 and the angle 6 for comparison of graphical and calculated results The following equations can be used to calculate these values 01 oxoy5oxoy24t 1 1 2 o2 oxoyE oxoy2410 0tan 231o oy PROBLEMS For this exercise construct a Mohr circle diagram for a twodimensional state of stress as shown by Figure 23 Two orthogonal and unequal compressional stresses acting at a point in a body with the resulting shear stress are given below 13 put 4 P u93 Given 5 o 6000 psi a 2000 psi ff 5 Q at quot d39z qr quotquotquot Problem 1 Construct the Mohr circle on Cartesian coordinate graph paper using the same scale for the 0 and 139 axes r 1 v a Measure the values of 01 02 and 6 from the diagram with a scale and protractor Using the appropriate equations confirm these graphical values Be careful to use correct signs b Convert the calculated psi values to SI units Nm2 or Pascals using conversion equations in Appendix 1 Q 3 Problem 2 The normal stress on and related shear stress rm should be measured from the diagram and calculated using the following equations o 3 C C is 0 p EXERCISE 2 Mohr Circle of Stress on o1o2o1 o2c0s26 rn o1o2sin28 V As might be expected from Figure 22 on and 7 equal 0 and 7 relative to the X and Y axes when the axes have been rotated 6 1 p at APPLICATIONS The relationship of this exercise to the real world is important In a natural setting as well as in laboratory testing of soil and rock samples the principal stresses are 01 02 and T3 The applied stress 0 in this case compressive is the stress required to cause material failure This value by de nition is the compressive strength of the sample The other orthogonal principal stresses U2 and 03 are the con ning stresses which in uence the value of 0 They are applied either by natural con nement in the eld or by laboratory equipment Thus the Mohr diagram can be used to show strength limits for eld stress conditions The influence of con nement on material strength and on the Mohr circle will be illustrated in Exercise 3 The normal stress on is the stress mobilized or generated perpendicular to a potential or an actual failure surface The shear stress 7 is the stress mobilized along the failure surface causing failure of the sample The relationships existing among the various stresses for different natural and experimental conditions are the subjects of Exercise 3 LOOKING AHEAD As we look ahead to Exercises 3 and 4 consider 1 why the Mohr diagram you constructed is representative of an uncon ned compressive test 2 where the circle would lie on the normal stress axis if the sample was con ned during compressional testing 3 what the Mohr circle diagram does not show about the response of a specimen to test conditions prior to failure Suggested References Additional information on Mohr circle construction and equations for solution of normal and shear stress values relative to the X and Y axes as well as the principal stress axes may be found in the following selected references Coates D F et al 1981 Rock mechanics grinci1a1 samp3v ed Ministry of Supply and Services Canada 401 pgs 12 Engineering Geology a Laboratory Manual Goodman R E 1989 Introduction to rock mechanics 2nd ed John Wiley amp Sons 562 pgs Herget G 1988 Stresses rock A A Balkema 179 pgs Hobbs B E W D Means and P F Williams 1976 An outline of structurageol ogx John Wiley amp Sons 571 pgs Hoek E and E T Brown 1980 Und round excavation in rock Inst of Mining and Metallurgy Canada 527 pgs Jaeger J C and N G W Cook 1979 Fundamentals of rock mechanics 3rd ed Chapman and Hall 593 pgs Johnson R B and J V DeGraff 1988 Principles of engineeringgeology John Wiley amp Sons 497 pgs I L 5Trz39axial testing by de nition requires stresses gt0 for all three principal stresses 01 02 and EXERCISE 3 TRlA3ALi TESTING pH AND MOHR DIAGRAMS he Mohr circle is useful as a graphical representation of the relationship between material strength and con nement during testing Exercise 2 dealt with an uniaxial or uncon ned case Triaxial testing utilizing one or more additional tests with different con ning stresses greatly enhances the usefulness of the Mohr circle Soils and rocks increase in compressive strength with increased con nement By plotting data from two or more tests the amount of strength increase can be seen on a Mohr diagram Figure 31 iquotquotK as 1 wasanr 03 It is mechanically dif cult to conduct true triaxial tests in which 02 and 03 are different As a result testing commonly is done by uniformly applying a con ning stress to the sample so that o2a3 The conventional designation of this stress is 03 as shown in Figure 31 Comparison of Figure 31 with Figure 23 of Exercise 2 reveals another convention that of displaying the positive shear stress half of the Mohr circle In Figure 31 all and 03 are the compressive strength and con ning stress major and minor principal stresses s T for an uncon ned test and 012 and of areww similar values for a con ned test It should be remembered that multiple tests such as 7 these which involve strength values result in 5 E0 5 destruction of each sample as failure occurs A Thus test samples of soil or rock should be selected to be as representative as possible of the material T 2 lt quot2 e 6 W go i Jquot I 03201 g Figure 3 Z e wwj At this point unique attributes of plotting multiple sets of test data become apparent especially for cohesive materials In Figure 31 a line tangent to each semicircle has been drawn and labeled failure envelope A line has been drawn horizontally to the shear stress axis from each point of tangency and labeled 7 and 7 respectively These are the shear strengths for the two tests shown The uniqueness of plotting compressional test results using Mohr circles is that the shear strength for each set of test conditions is obtained graphically Thus compressional testing of a sample provides an indirect means of obtaining the shear strength of a material This is of special importance because materials actually undergo shear failure at the point of failure under compressive load The Mohr diagram graphically displays both compressive and shear strengths 13 14 Engineering Geology a Laboratory Manual 01 and Tf Shear strength 7 is used as a notation rather than 7 because it is a limiting case of 7 at failure and represents the shear stress on the failure surface at failure Another feature of triaxial Mohr circle diagrams is the failure envelope itself If the tangent point is the shear stress strength at failure any crossing of the line caused by an increase in 01 or reduction in 03 would represent failure or rupture of the sample thus the name In actual testing multiple test samples typically result in a failure or rupture envelope that is slightly convex upward It is normal practice to construct a straight line averaging the locus of tangent points for multiple circles This line to be correct is the MolirCouloml failure envelope as its linearity was de ned by Coulomb As noted above failure during a compression test uniaxial or triaxial occurs as a shear failure Figure 32 is a two 71 dimensional diagram of a test sample at the point of failure We L can see three familiar parameters on the diagram 0 T3 and 7 In Figure 22 of Exercise 2 there is a normal stress 03 acting perpendicular to the shear stress 739 and the potential shear failure plane This normal stress component of 0 acts in the same fashion during actual testing The shear failure surface or plane always occurs at some angle to both principal stresses shown in the gure These angles are or and 6 shown on the gure If you use a variety of sources of information for your course you may find that 0 and 6 are reversed from those T shown here This is just a notation change but the change must be carried through to the use of these angles on a Mohr diagram The angle 3 as used in Figure 32 also is the angle between 0 and an Thus oz 6 90 Figure 32 With this information derived from a sample undergoing compressional strength testing we can return to the Mohr diagram to compare the remarkable relationship this graphical representation of test data has to stresses and angles during actual testing Figure 33 displays these stresses and angles for a triaxial test It is similar to Figure 31 where 73 is 7 in Figure 33 All angles and notations shown on Figure 33 can be applied to the smaller uncon ned test semicircle Do not try to compare the actual measured values of angles with those Shown on Figure 32 This can be done when using 0 actual test data However each material s so strength properties will generate different 0 D 25 angles of shear plane orientation etc For r U G 2 O U 0 example if 6 increases oi will decrease 3 quot rrf crn ton c r i 4 O0 O1 quotU32 The normal stress on acting on the failure 061 3 2 23 T U quot0 4 Sin surface at the moment of failure also is G G 032440 U 60325 shown on Figure 33 This stress is only quot H 3 3 9 cos TOci shown diagrammatically on Figure 32 On zcp2 45 the Mohr diagram it has a de nite value for each test It is always the perpendicular to Figure 33 n n n EXERCISE 3 TriaxiaITestingandMohrDiagrams 15 the normal stress axis from the point of tangency a on Figure 33 An additional angle is shown on Figure 33 The angle qb is the angle between the failure envelope and the horizontal It is the angle of internal friction or friction angle and it varies proportionally with the increase in strength of a sample as or changes It plays a major role in the 3 shear strength of a material for a given amount of con nement It may be thought of as a measure of the frictional resistance a given material has to shear failure The angle qb is less for soils compared to most rocks but the proportional reductions in compressive strength and con ning stresses in soil samples may cause the angle to overlap the lower range obtained for rocks The cohesion c of the material being used for this example is shown graphically on the shear stress axis 7 Cohesion is an inherent property of a material independent of stresses As seen in Figures 31 and 33 it contributes to the shear strength of a cohesive material such as clay Noncohesive cohesionless materials such as sand exhibit zero cohesion by de nition In these materials the failure envelopes resulting from triaxial tests intersect the 7 axis at zero For cohesive materials the shear strength is related to 0 d5 and c This relationship is shown on Figure 33 by the equation 39rfor tan qb c The equation often is referred to as Coulomb s equation Equations for the semicircles and variables are shown on Figure 33 If you compare variables used in this exercise with those shown on Figure 23 of Exercise 2 you will nd that the angle 459 and a 0 and 39r39r for the limiting case of the point of tangency of the failure envelope with a Mohr circle Values of or have been seen to vary proportionally with changes in the con ning T l s stress 03 Water in undrained porous soils a e ectively reduces the values of a and 03 by an amount equal to the pore water pressure while retaining the proportional differences between them This is shown graphically by Figure 34 a Mohr diagram of a con ned compression test on a noncohesive soil The gure shows the effective reduction in compressive strength Note that the material strength is not changed relative to a given con ning stress However the lowering of the con ning stress 03 by the value of p Figure 34 does in turn result in an equal reduction in the compres mi wig material failure The gure also graphically illustrates the L 7 m strength 7 caused by pore pressThe failure envelopes and associated friction angles also are affecfed y o i sre ubscript u for the total stress envelope denotes an undrained state during testing The new stresses are called effective stresses or and are equal to 0 a u where cr can be any of the three principal stresses Ppre pressure it is dealt with in greater detail in Exercises 12 and 16 p M PL 5 E a f quotfrx quot W quot t l quot39 sf 39 nan2 M g F PROBLEMS P The problems for this exercise consist of constructing Mohr diagrams for uniaxial and triaxial data for soil and rock tests given below After construction of the diagrams the angle of internal 16 Engineering Geology a Laboratory Manual friction cohesion and shear strengths will be determined for each Comparison of selected graphical and calculated values of the same parameter will be made Use of 10 divin graph paper is recommended for construction of the diagrams 39 av J a I 2 m far quot J I Gwen v P1v v zl rQr Ev Iggt v Problem I data set Problem 2 data set 0 quotquot quotquot 39 i39 quot quotiquot r39 p 5 S011 test datasilty clay Rock test data gran1te o A stresses in psi stresses in psi x 1000 R T R gr 2 U1 03 71 73 Test 1 70 10 Test 1 310 0 p Test 2 98 Test 2 450 2 03 Test 3 155 Test 3 672 5 l e3 u 0 Procedure t 5 1 p if Zquot J55 C T o iJ s 1 Draw er and r axes for e er lq am using data from problem data sets 1 and 2 with 1 in20 W psi for soil data and l in l93 103 psi for rock data Use the same scales for the normal stress and shear stress axes for a given diagram Construct semicircles for each set of data using equations in Figure 33 to obtain center and i quot radius of each semicircle Jf39I ii3Draw a tangent line to the semicircles for each set of test data If construction is correct each quoti line will be tangent to its semicircles i4EUsing a protractor measure and label the friction angle qb for each set of data Draw the shear strength lines for each test in each set of data to the shear stress axis label Lb each test 739 etc and tabulate shear strength amounts on your diagram Label cohesion c and enter value for each set of data with answers to step 5 i 3939 P Draw the normal stresses on the normal stress axis for each test label and tabulate values with preceding results A 39 Select Test 3 for the soil sample and the rock sample and Gaiil ulate shear strength 1 for each test using the equation 7cr tan gs c Use the measured values of lt13 and c and the calculated value of an xixffiij 0H Draw a diagram similar to Figure 32 labeling values for all angles and stresses for the rock S 3 test data used in step 8 above ii EXERCISE 3 Triaxial Testing and Mohr Diagrams 17 i lQ5ketch a Mohr diagram for a triaxial test of a noncohesive S01l such as a sand and explain the reasons for your construction ltiflConsider what effect a pore pressure of 15 psi will have on the triaxial soil data given for t test 3 in the problem 1 data set Using your Mohr diagram for problem 1 construct an effective stress semicircle and compare it to the test 3 Mohr circle What effect have the effective stresses had on the shear strength of this soil at the stress levels given in test 3 g A QM ILE3 thy aid J QUESTIONS quot 1 Compare the graphic and cgillculatedllvaliiexr for 7 obtained in Procedure step 8 Which do you think is more accurate and why Na d i 2 Note how the shear strength of each material increases with con nement Of the factors governing shear strength given in equation ra tan q5 C which is are controlled by the material and which by the site conditions aridkpihy wt gsif eewiihtwav I 3 Assume a condition in which a rock mass acts as an intact joint free rock such as that used for the problem 1 data What would happen if tunnel construction exposed the rock for the conditions shown by test 3 at W Q in WW9r quotf iquot Mne g ms quot z7 39EmquotlM 39W 9quotquotquotquot W 4 How might you be able to monitor the pore pressures at a potentially unstable soil hillslope Triaxial testing of soils and rocks provides information about the ranges of principal stresses which govern shear failures in materials free of joints wellde ned bedding foliation faults and G similar surfaces which disrupt an intact material These surfaces are included in the nongenetic p E J term discontinuity At any point at which the compressional load andor confining loads qqJi combine to create a semicircle which crosses the shear failure envelope one can expect failure 57 4 within the material Soil masses usually are discontinuity free and react as a relatively 439 ihomogeneous mass Conservative design of engineering structures in soils requires that stress conditions in the material be kept well below those that are tangent to the failure envelope At this point you may have foreseen the in uence of pore pressure on the stability of soil slopes Moistu in soil masses is a major contributor to slope failure Of the preventive or remedial measures available in areas of unstable soil slopes reduction of water content and resulting lowering of effective stress ranks at or near the top of available procedures The reduction in water content is achieved by improvement of drainage ranging from pumping of a system of dewatering wells to diversion of surface water Rock mqsses by comparison are usually characterized by one or more kinds of discontinuities wuhi cahmgreatly affect the predictability of failures Depending upon their orientation discontinuities may be the primary cause of rock mass failure with failure occurring at shear stresses well below those required for intact rock failure APPLICATIONS F 18 Engineering Geology a Laboratory Manual The presence of foliation in a metamorphic rock introduces potential failure surfaces in what otherwise may be a relatively intact material One would thinkthat the orientation of greatest weakness is where foliation orientation is parallel to the principal compressive stress 0 However an examination of Figure 32 causes us to rethink the prevailing conditions The greatest shear stress that leads to failure is oriented at the angle or to the 0 axis Thus in a proposed road cut in rock orientation of foliation relative to both the vertical rock load on the rock mass and the proposed cut slope orientation are of major importance If the foliation dips toward the road cut failure is more likely to occur than if it dips in any other direction the safest orientation being into the slope Well de ned discontinuities in metamorphic rocks such as joints typically have a greater influence on stability than foliation LOOKING AHEAD As we have shown Mohr circle diagrams provide known ranges of loads before failure occurs in discontinuityfree materials Useful as they are they do not show any material deformation strain that takes place when a material is subjected to loads The strain that may occur at a construction site during and after construction is of vital importance when designing large structures such as dams and support structures as in tunnel construction The testing that gave us the kind of data used for this exercise can provide the strain data at stress application increments as a sample is loaded to failure in either the uncon ned or confined state Exercise 4 will provide an opportunity to examine the deformability characteristics of a material and the elastic properties that are of importance in the design of engineering structures in earth materials 7X K Several soil parameters that affect the values of qb d cg Flie s a fe paricle size particle grading grainsize distribution moisture content void rt tio a rn asure of porosity particle friction and shape Several of these are examined in greater detail in Exercises 1112 and 13 In Exercise 16 the role of effective stress in soil slope stability is covered References Cited Coates D F et al 1981 Rock mechanics pringipleg rev ed Ministry of Supply and Services Canada 401 pgs Dennen W H and B R Moore 1986 Geogv andggineerin r Wm Brown Publishers 377 pgs Franklin J S and M B Dusseault 1989 Rock engineering McGraw Hill 600 pgs Herget G 1988 Stresses in rock A A Balkema 179 pgs Hoek E and E T Brown 1980 Und round excavations in rock Institution of Mining and Metallurgy 527 pgs Hunt R E 1986 Geotechnical engineering techniques and practice McGrawHill Book Co 729 pgs Jaeger J C and N G W Cook 1979 Fundamentals of rock mechanic 3rd ed Chapman and Hall 593 P85 Johnson R B and J V DeGraff 1988 Principles of engineering geolgy John Wiley amp Sons 497 pgs Rahn P H 1986 Engineering geology an environmental zygproach Elsevier 539 pgs EXERCISE 4 ROCK STRENGTH AND MODULUS OF ELASTICITY n Exercise 3 the in uence of con ning stress on the compressive strength of a soil or rock I sample was examined By using Mohr circles to plot the data you were able to graphically determine the shear strengths mobilized along the failure plane for various con ning stresses as well as the normal stresses to the shear plane While useful in determining safe levels of applied stresses for given con nements during construction Mohr circle analysis does not provide defamation data for a given uniaxial or triaxial test Axial and lateral deformation of a soil or rock under loading is usually of greater value in the design of a structure than the stresses at failure Conservative design criteria typically keep applied stresses below failure stresses Stressstrain graphs provide data on elastic and plastic deformation of materials under compressional loads prior to failure The required data are obtained during testing for Mohr circle analysis by measuring the axial forces or loads applied to the sample and the resulting changes in length of specimens prior to failure Stress values 0 are calculated as de ned and used in Exercises 2 and 3 In this exercise when or is used without a subscript it will refer to 01 as in Figures 415 Strain e is a measure of plastic and elastic deformation caused by a given applied stress It is a unitless value because it is a measure of change in length per unit length ie inin or cmcm It can be expressed as a percentage Figure 41 is a plot of Strain e axial deformation data for a rock sample showing the Figure 41 stress and strain axes without numerical values Stress cr Strenth as de ned in earlier exercises on the Mohr circle is the compressive stress 01 at failure It is shown Squote 9th5treS5 t f quot 39e F i i y p graphically on a stress strain plot if the test is continued F I W to sample failure as in Figure 42 The strength of a quotFig material is dependent on the rate of axial compressive stress application for a given amount of con nement Rapid loading of the specimen results in increased strength compared to slower application rates In Exercise 3 it was shown that as con nement of a sample increased there was a proportional increase in strength Most rock mass classi cations used in evaluating rock mass quality at a construction site utilize uncon ned Smin Stress0 19 Figure 42 20 Engineering Geology a Laboratory Manual can be altered by varying the load application rate and amount of con nement such classi cations would be of questionable value without some degree of testing uniformity That uniformity is obtained by always using strengths from uncon ned testing and an accepted rate of stress application The International Society for Rock Mechanics ISRM suggests a stress application rate of 0510 MPasec ISRM 1979 In this exercise strain is axial compressional deformation caused by application of 01 for different values of U2 and 03 As noted in Exercise 3 a2 03 for most triaxial tests The elastic portions of stress strain plots are linear showing a constant relationship between stress and strain for the given test conditions Ideally this elastic deformation is recoverable as stress is reduced Modulus of elasticity and Young s modulus are synonymous terms for the measurement of elasticity of a material expressed as E The modulus of elasticity is the most useful of several elastic moduli others being Poisson s ratio shear modulus and bulk modulus Only the modulus of elasticity will be examined in this exercise Figure 43 illustrates the linear segment of the stress strain curve used to obtain E The non linear portion of EzstressStrmnzg5 the curve is non recoverable deformation generally classed as plastic or ductile strain although the defor mation adjacent to the origin actually is from closure of cracks etc in the intact sample upon application of compressive stress Stress 039 m As might be expected the modulus of elasticity E is affected by stress application rate and specimen con nement Increases in either result in increased 2 values for E Testing conditions for determining the J elastic modulus are suggested by the ISRM Note that Stroin e the commonly used term elastic constant is not Figure 43 appropriate if tests are not conducted according to uniform standards Even if testing is performed according to uniform standards strength and the modulus of elasticity are not constants for a given rock site A reason for this is that a test which continues to sample failure is a destructive test which cannot be repeated on the same sample Rock texture fabric mineralogy cementation etc will differ from one sample to another in the same rock unit This precludes any truly reproducible test results Thus lithology introduces reasons for lack of data reproducibility in addition to those imposed by testing conditions it In engineering practice where structures or excavations can be affected by earth material PS deformation before durin r after constguction two values of modulus of elasticity are calculated These are the Eangent modulus Ff and the The standard for 5 calculating these moduli is 0 of the strength a value that ideally places the modulus value E50 and Em at an optimum value of elasticity For practical purposes the tangentgt mod us Figure 44 will be the same as the value obtained by calculating E as shown in Figur E 42 The tangent modulus provides deformation data for a sample with the assumption that thesample responds elastically from the onset of compressive stress application It is therefore not a true indicator of the sample s deformation response to loading The secant modulus Figure 45 by uniaxial compressive rock strength as one parameter If the strength of a representative sample EXERCISE 4 Rock Strength and Modulus of Elasticity 21 comparison takes the nonelastic deformation that occurs as a load is applied into consideration It L 30 ning E50 U ijs therefore a yServa 1 v e E ir1sdLcator of d e f o r m a t i o n which can be applied to the 4 S troin d e Sig n O f Stroin structures which Figure 45 must tolerate d e f o r m a t i o n resulting from construction Both moduli combined with Mohr circle plots utilizing estimated stresses are useful in predicting deformation and potential rock failure resulting from excavation of rock having high natural or in Sim stresses from mountain building forces andor igneous intrusions Listings of typical rock strengths and modulus of elasticity values can be found in Rahn 1986 Johnson and DeGraff 1988 Franklin and Dusseault 1989 Wyllie 1991 and Bell 1992 T9999 modulus Of BJGSHCHY Secont modulus of elasticity 5 strength StressU Stress cI Figure 44 PROBLEMS Determine the strength and the moduli E50 and E550 for an uncon ned compressiont1 E 5Stg on an intact sample of rock It will be necessary to convert the loads and changesir en thjof the sample to stress and strain values All data necessary for these conversions a1equotquot givquotenbel t 5w Use Cartesian coordinate paper ruled at either 10 or 20 divin for the problem When determining the linear elastic portion of the plot do not expect all points to fall perfectly on a straight line These are real data and therefore draw a best linear fit to the points in the midrange of the plotted points It may be necessary to increase the strain scale x axis to separate out the non linear portions of the curve obtained early and late in the testing g W E ivwrrt amp es Ev Given I Siltstone cylinder 415 in long and 210 in diameter ea H gag aw a c I Uncon ned compression test data 111 Table 41 P e uwd Ettw Problem I v39wVs quot is PH wit 3 aMuas 5 E4 5 Convert load values in Table 41 to psi and change in length values to inin Problem 2 Construct a stress strain diagram similar to Figure 41 22 Engineering Geology a Laboratory Manual V Problem 3 Determine the rock strength in psi if Problem 4 Calculate the tangent and secant moduli in psi Problem 5 Convert answers to Problems 3 amp 4 into SI units Pa or MPa or GPa whichever are appropriate Table 4 1 Load Change in Load cont Change in lengthquot 1 lengthcont 0 0 15000 41 1 1000 46 16000 435 2000 83 17000 45 9 3000 117 18000 483 4000 147 19000 507 5000 I 171 20000 531 6000 195 21000 555 7000 219 22000 r 577 8000 243 23000 603 9000 267 24000 627 10000 29 1 25000 65 1 11000 315 26000 677 12000 39 339 27000 701 13000 363 28000 741 14000 387 28500 764 failure in lbs in 0001 in Q UES TIONS 1 Testing for this exercise was done on an uncon ned intact sample How representative do you think your values of elastic moduli are when estimating possible elastic unloading of rock stresses and resulting deformation in an underground quarry in this rock EXERCISE 4 Rock Strength and Modulus of Elasticity 23 2 What rock mass characteristics would cause you to be skeptical of using datafrom testing intact samples even if in Sim stresses were duplicated Ag a s t392 m vai3b i4 3 Can you think of a way to obtain more representative measures of rock mass deformation at the site as opposed to intact rock testing in the lab 4 What are some engineering structures where loading natural construction or in service causes rock mass deformation 5 Underground construction of mines tunnels and powerplants will relieve confining stresses to an unconfined state at the rock faces exposed by construction What potential problems will there be during and after construction as stresses are relieved APPLICATIONS Strength and deformability of rock samples are important parameters in many civil engineering applications Uniaxial strength of such intact samples is included in most rock mass classi cations which in tum are used to characterize rock mass conditions present in tunneling construction and surface excavations Rate of tunneling or excavation required equipment and design of rock support are all affected by classi cation data Abrasion resistance of natural and crushed stone aggregate during and after construction is controlled in part by rock strength Strength is also related to physical and chemical weathering of rock Measures of intact rock deformability such as the modulus of elasticity examined in this exercise are critical to predicting rock deformation or failure during construction in hydrostatically or tectonically loaded rock masses as con ning stresses are lowered or removed In addition loading of a rock mass by such things as surface structures or by highpressure water tunnels in the subsurface creates rock mass deformation that can be estimated by knowledge of intact rock deformability LOOKING AHEAD In Exercise 6 less costly and time consuming tests of rock strength will be examined The use of quick simple tests to obtain measures of strength bears witness to the importance of strength in design and construction of structures in rock Tangent and secant moduli of elasticity were obtained in this exercise as a part of obtaining the strength of a sample Uniaxial uncon ned and triaxial con ned strength testing of rock specimens are classed as static tests which are destructive tests Determination of the deformation characteristics defined by the modulus of elasticity by non destructive means is desirable in many cases Dynamic testing of samples by passage of shock waves through them is non destructive and the results provide a measure not only of the modulus of elasticity but also a measure of strength which is correlated to elasticity Exercise 5 provides an opportunity to become familiar with dynamic testing and its advantages and disadvantages 24 Engineering Geology a Laboratory Manual Propagation of seismic shock waves through earth materials is dependent on elastic properties of the materials involved Seismic exploration of the subsurface is possible because of the elastically controlled shock wave velocities which characterize different soil and rock units Greater insight into the elastic properties of materials and the factors controlling both elasticity and seismic velocities will be gained upon completion of Exercise 19 Engineering Geophysics References Cited Bell F G 1992 Engineering properties of soils and roclig 3rd ed ButterworthHeinemann 345 pgs Franklin J A and M B Dusseault 1989 Rock engineering McGrawHill 600 pgs ISRM 1979 Suggested methods for determining the uniaxial compressive strength and deformability of rock materials Intl Soc Rock Mech Comm on Standardization of Laboratory and Field Tests Intl J Rock Mech Min Sci amp Geomech Ahstr v01 16 pp 135140 Johnson R B and J V DeGraff 1988 Principles of engineering geolgyz John Wiley amp Sons 497 pgs Rahn P H 1986 Engineering geology an environmental approach Elsevier 539 pgs Wyllie D C 1991 Foundations in rock E amp F N SPON 331 pgs EXERCISE 6 ltIND Ex g OF INTACT ROCK ndex tests are tests which provide data that are indicators or indices of important I engineering properties of rock They are not designed to replace more time consuming and costly testing but they do permit quick assessments of rock properties so that better decisions can be made concerning more detailed testing Strength hardness resistance to abrasion and slaking characteristics are rock properties for which there are index tests Two index tests which are indicators of uncon ned compressive strength of rock are the subjects of this exercise These are the point load test and the Schmidt rebound hammer test or Schmidt hammer test The point load test is a destructive test resulting in breakage of the sample When used properly the Schmidt hammer test does not cause rock breakage Point load test Point load test equipment consists of two types nonportable laboratory equipment and portable equipment which can be used in the eld or laboratory The point load test as its name implies involves Pressure pd applying force to a sample by two opposing Hydraulic gouge ploten conical platens as shown by Figure 61 The Om W119 Movegble result of this force application is tensile quot P ac failure of the rock sample The maximum pressure recorded by the test equipment at sample failure is used in calculating the L index value 1 or the uncorrected point load strength in psi or Pa This index the point load index 1 is obtained from the following equation Figure 61 where p applied load in lbf or N d distance between platen points in appropriate units The term uncorrected point load strength used above with the point load index indicates the need for correction for calculation of 1 It should be apparent that the force P will be dependent on the size of sample D all rock properties remaining constant The ideal size and shape of 29 30 Engineering Geology a Laboratory Manual samples for which no corrections are necessary are a 50 mm diameter cylinder core ideally having a length to diameter ratio gt 10 The commonly used NX core size of 54 mm is considered to be within the error limits for a 50 mm diameter sample and can be used without correction Variations in shape from the ideal circular cross section also require correction If I is to be used to estimate uncon ned compressive strength it first must be corrected by an empirically derived multiplier to convert 1 values to strength in psi or Pa A multiplier of 24 is commonly used to convert I for a 50 mm diameter core sample to strength units Details of and the need for the corrections noted above as well as information about test equipment and testing procedures may be found in Broch and Franklin 1972 Bieniawski 1975 ISRM 1985 Johnson and DeGraff 1988 Franklin and Dusseault 1989 and West 1991 Table 61 lists rock types 1 values and corresponding compressive strengths for the samples A multiplier of 24 was used to obtain strength from 1 Index and strength values are given in SI units All samples were isotropic eld samples and required size and shape corrections prior to use here Examination of Table 61 reveals the expected correlation between rock type and 1 Sandstone and siltstone typically exhibit wide ranges in strength resulting from differences in grain size distribution and amount and kind of cement Table 61 T T Rock type i 1 MPa Strength MP0 I Fine grained quartzose sandstone 6208 39 149 Fine grained quartzose sandstone 3458 83 Siltstone 8542 205 Clastic limestone 5958 143 Clastic limestone 7292 175 Micritic limestone 5583 134 Medium grained quartzose sandstone 4000 96 Mediumgrained quartzose sandstone 2500 60 Coarsegrained granite 5167 124 When any necessary corrections have been made I can be used to estimate rock strength with further correction or it can be used directly in rock classi cations as a strength index Bieniawski 1989 has assigned 1 value ranges to the intact rock strength classi cation of Deere and Miller 1966 The Deere and Miller classi cation is one of several in use there being only minor differences among them for strength ranges Table 62 provides 1 ranges of values for the strength ranges and associated strength categories of Deere and Miller A visual comparison of the Is and strength values in Table 61 permits placement of the samples tested into rock strength categories The following references deal with the use of the point load index 1 in estimating strength and their use in rock classi cation Bieniawski 1989 Franklin and Dusseault 1989 Cargill and Shakoor 1990 EXERCISE 6 Index Tests of Intact Rock 31 Table 62 i Categog L Strength 251 Strength MPa i I Very high gt 32000 gt 200 gt 10 High 1600032000 100200 410 Medium 800016000 50200 24 Low 40008000 25 50 12 Very low lt4000 lt 25 A lt 1 Schmidt hammer test Hardness of rock has been associated with its strength for many years Most of us are familiar with the differences in the sound or quotringquot resulting when a rock is struck with a rock hammer The harder the rock the sharper the ring and vice versa Coincident with listening to the sound of a hammer on rock is the amount of rebound of the hammer upon striking the rock surface and the degree of physical change occurring at the point of impact Harder rocks result in greater rebound while softer weaker rocks may absorb the blows so such a degree that there is little or no rebound of the hammer Breakage or indenting of rock when struck occurs in medium to weak strength rocks These responses of rock to hammer blows as well as to scratch tests have been used in several intact rock strength classi cations Piteau 1971 Geological Society 1977 Williamson 1980 Franklin 1986 Williamson and Kuhn 1988 Williamson s rock classi cation used by the USDA Forest Service relates strength to surface changes resulting from blows by a ball peen hammer Table 63 Table 63 Rock ace r blow Stren th 39 Stren th MPa No change gt 15000 gt103 Shallow rough pit 800015000 55103 Dent or depression 30008000 2155 Cratering with rim 10003000 721 The Schmidt rebound hammer was designed to standardize both the methodology of hardness testing and the force with which a hammer strikes a rock surface As a result the measured amount of rebound can be correlated with the rock strength in much the same way as with point load data In this case however the amount of rebound is actually a measure of the material s elasticity which is reflected in its hardness In addition there was the need for a small hand held instrument for use in the eld as well as in the lab The Type L Schmidt hammer used in engineering geology applications was speci cally developed to determine the hardness and thus strength of Portland cement concrete in the lab and at a construction site Deere and Miller 1966 were among the rst to utilize the Schmidt hammer for rock hardness and related strength Field and laboratory standardization has been de ned by the International Society of Rock Mechanics ISRM 1978 Use of the Schmidt hammer is described in Johnson and DeGraff 1988 Franklin and Dusseault 1989 and West 1991 32 Figure 62 illustrates the Type L hammer in use on the surface of one of the sandstones listed in Tables 61 and 64 Orientation of the hammer affects the results because gravity in uences the controlled impact of the hammer mass on a surface Care should be taken to maintain a consistent orientation especially when it is used in the eld Most of the references given in the preceding section on the point load as well as those in this section include sections on Schmidt hammer use and interpretation should you have access to one for either lab or field testing The numerical results of Schmidt hammer testing are percent values of an ideal 100 rebound Figure 63 shows a reading of 41 taken on sone of the sandstones in Table 64 Table 64 lists the same rock units from which the point load values were obtained in Table 61 The Schmidt hammer values SHV reveal a fair degree of scatter relative to the compressive strengths This is common to the method and especially so in eld use where orientation may not be maintained precisely All test results shown were obtained from surfaces with roughness removed so that the hammer impacted a smooth planar surface Engineering Geology 21 Laboratory Manual Figure 62 Photo bD Zavadil Figur 63 Pho by D Zavadil Table 64 R0gaQyger T y SH V rStrergth MPO Finegrained quartzose sandstone 478 149 Finegrained quartzose sandstone 399 83 Siltstone 459 205 Clastic limestone 406 143 Clastic limestone 467 175 Micritic limestone 444 134 Medium grained quartzose sandstone 440 96 Medium grained quartzose sandstone 450 60 430 124 Course grained granite 4539 EXERCISE 6 Index Tests of Intact Rock 33 PROBLEMS In this exercise data from a point load test will be used to calculate IS and the uncon ned compressive strength Assignment of the sample to one of Deere and Miller s strength categories will be made Data from Tables 61 and 64 will be plotted and comparisons will be made among the tests and rock types R R Given S NX core diameter D 54 mm Table 61 data I I Load P at failure 104 x 10 KN I I Table 64 data Problem I U V at Ma Calculation of Is 0 O be at E E l P B a Solve for Is note that the pressure readout on the equipment is in kNC0nvert L EM t0 Nfiefolf 91iiDg lt17011 mG ii iiiiiii p J H J m hK 5 r lJMm i wb wig R5 Elk H N 5 3 I 7H s a 4 if Wig Wei 0 H quotquotquotT G T W quot9 Problem D NiI p1 6quot Q or gt gee G teem quot G jE re 6 K Calculation of uncon ned compressive strength a Use a multiplier of 24 to convert Is to strength b Convert strength in MPa to psi M ggmk Assign the sample to one of the strength categories given in Table 62 aquotquot 1 1 39 397 quotquotquotquotquotquotquotquotquotquotquot INN 5 i Problem 3 F WWM Graph the point load test data in Table 61 a Use compressive strength as the independent variable b For x axis use lquot40 MPa 4 c For y axis use 1quot 2 MPa F 39 d Optional calculate and construct a regression line using equations provided y b x3 your instructor i quot j i5 quot i i 2 ran 39 N Problem 4 RE Graph the Schmidt hammer data in Table 64 a Use compressive strength as the independent variable b Use the same x axis scale as in part 3 b above c Use 1quot 10 SHV units on the y axis k d Optional calculate and construct a regression line for these data as in part 3 d above Bf 34 Engineering Geology a Laboratory Manual QUESTIONS 1 Why was there no correction required when calculating L 2 Is calculation of strength from L necessary for assignment of the rock sample to a given strength category 3 Why is I a better indicator of rock strength than the calculated value of strength 4 The plot of compressive strength vs I shows the expected linear relationship The sandstone samples show considerable differences in I and strength amounts Give two reasons for these differences 5 The plot of compressive strength vs SHV shows the expected increase in SHV with increases in compressive strength However the scatter is considerable but consistent with Schmidt hammer testing especially when done in the field as was the case here Can you think of a reason for the scatter of this plot when compared to the point load data plot APPLI CA T I ONS There is considerable need for quick index tests that can be made either at a site or in the lab The reliability of the point load test in estimating uncon ned compressive strength is of value prior to and during construction where strengths are required when planning the use of explosives use of tunnel boring machines TBM etc Values of I are more representative of strength than are the strengths calculated from them because of variations in the multiplier amount Thus they are used directly during planning of construction in rock as well as in some rock mass classi cations such as the geomechanical rock mass rating classi cation of Bieniawski 1989 The Schmidt hammer provides less reliable measures of rock strengths However rock hardness in addition to intact strength is a major factor in the performance of drill bits and TBM operation The hammer s small size and its use directly on a rock surface make it an ideal tool for making quick estimates of intact rock properties at a construction site without having to make corrections LOOKING AHEAD Rock strength and hardness as determined in part by point load and Schmidt hammer testing are factors in estimating abrasive wear characteristics of aggregate crushed stone and gravel Shearing of rough surfaces during rock movement along joints and other discontinuities involves the strength of the rough projections asperities The friction mobilized along such a surface is a factor considered in Exercise 9 where rock slope stability is investigated EXERCISE 6 Index Tests of Intact Rock 35 References Cited Bieniawski Z T 1975 The point load test in geotechnicalpractice Eng Geology Vol 9 pp 111 1989 Qineering rock mass classi cations John Wiley amp Sons 251 pgs Broch E and J A Franklin 1972 The pointload strepgth test Intl J Rock Mech Min Sci amp Geomech Abstr Vol 9 pp 669697 Cargill J S and A Shakoor 1990 Evaluation of empirical methods for measuring the uniaxial compressive strength of rock Intl J Rock Mech Min Sci amp Geomech Abstr Vol 27 pp 495503 Deere D U and R P Miller 1966 Engineering classi cation and index properties for intact rock Tech Rep No AFWLTR65116 Univ of Illinois Urbana 299 pgs Franklin J A 1986 Sizestrength system for rock chaaracterization pi Application of rock characterization techniques in mine design AIME pp 1116 Franklin J A and M B Dusseault 1989 Rock engineering McGrawHill Book Co 600 pgs Geological Society 1977 The description of rock mass for engineeringpurposes Geol Soc London Eng Group Working Party Q J Eng Geol Vol 10 pp355 388 ISRM 1978 Suggested methods for determining hardness and abrasiveness of rocks Intl Soc Rock Mech Comm on Standardization of Laboratory and Field Tests Intl J Rock Mech Min Sci amp Geomech Abstr Vol 15 pp 8997 1985 Suggested method for determining point load strength Intl Soc Rock Mech Comm on Testing Methods Intl J Rock Mech Min Sci amp Geomech Abstr Vol 22 pp 5160 Johnson R B and J V DeGraff 1988 Principles of engineering geology John Wiley amp Sons 497 pgs Piteau D R 1971 Geological factors signi cant to the stability of slopes cut in rock S Afr Inst Min Met Symp o the Theoretical Background to Planning of Open Pit Mines Johannesburg pp 3353 West G 1991 The eld description of engineering soils and rocks John Wiley amp Sons 129 pgs Williamson D A 1980 Uniform rock classi cation for geotechnical engineering purposes Transp Res Rec 783 pp 914 Williamson D A and R Kuhn 1988 The Uni ed Rock Classi cation in Rock Classi cation Syustems for Engineering Purposes Am Soc for Testing and Materials Spec Tech Pub 984 pp 716 Wyllie D C 1991 Foundations on rock E amp FN SPON 333 pgs EXERCESE 7 cone Loss AND ROD E xercises to this point have dealt almost exclusively with intact rock In Exercise 3 you were introduced to the terms rock mass and discontinuity A rock mass is a volume of rock which is divided into blocks or layers by discontinuities Discontinuities such as bedding surfaces joints foliation and faults greatly reduce the strength of a rock mass compared to the strengths of intact samples from that same rock mass Deformability of a rock mass and its causes were addressed in Exercise 4 When the term rock mass quality is referred to in an engineering context it refers to the quotabilityquot of a rock mass to perform certain design requirements For example the quality requirements of a rock mass occurring as a dam foundation are different from rock which will become the roof of a tunnel under construction Most rock mass classi cations began as a means of describing or characterizing rock masses for design construction and safety of tunnels Tunnel and other underground construction typically have greater need for predicting quality than other engineering structures Design and construction of rock cuts for transportation corridors and open pit mines probably rank second The simplest indicators of rock quality at a site are the rock types presence and characteristics of discontinuities and degree of chemical weathering or decomposition Major engineering structures in rock such as tunnels underground power plants and large dams require more information about the subsurface than can be gained by extrapolation from the surface As a result rock cores are obtained from drill holes that penetrate the rock mass where construction will occur or into zones potentially susceptible to rock mass deformation andor water flow during and after construction It was from drill holes such as this that the specimens tested in Exercises 36 were obtained When coring is done the length of rock cored usually the length of the core barrel is known The core is measured and described after removal from the core barrel If the measured length of core is less than the length cored there is core loss which can be represented either as per cent of the total core length recovered or percent lost Any core loss and where it occurs in a cored interval need to be explained the greater the amount the greater reduction in rock mass quality The reason for this is that rock not recovered or too broken up to measure represents zones of closely spaced discontinuities andor chemical weathering When these zones occur where construction will take place significant changes in construction must be made for reasons of safety as well as determination of construction methods Thus core loss or core recovery has been used for many years as a crude measure of rock quality Figure 71 illustrates a 10 ft core in granite Locations of core loss CL are shown In the section labeled quotno core lossquot the 36 EXERCISE 7 Core Loss and RQD 37 core had been broken and could be tted together The core appears to have a high core recovery percentage from visual examination Let us consider that we have 100 core recovery At the outset it would appear that we have excellent rock quality However we might have cored through a zone having closely spaced discontinuities in rock strong enough to endure destruction during the drilling operation It would be folly to assign to the rock such a high quality under these circumstances This was recognized by Deere et al 1967 who devised a modi ed core loss measurement called Rock Quality Designation or RQD to account for not only the true core loss but to add to it all thin pieces 5 it which contribute to a reduction in rock mass Figum 71 quality They arbitrarily chose a 4 in 10 cm length of core as the basis for measurement Only those pieces of core greater than or equal to 4 in are measured totaled and divided by the total length cored Pieces with acute angle contacts are measured along the centerline as shown by the line in the bottom row of core in Figure 71 RQD visually appears to be signi cantly lower than core recovery Studies have shown an expected inverse linear relation between RQD and the frequency of discontinuities or quotfracturesquot in rock Fracture as used here is a commonly employed loosely de ned term that includes all kinds of discontinuities RQD percentages are related to rock quality and estimated spacing amounts in Table 71 Table 71 RQD ROCK QUALITY FRACTURE SPACING 025 Very poor Very close 2550 Poor Close 5075 Fair Moderately wide 7590 Good Wide 90100 Excellent Very wide RQD was developed exclusively for use with rock cores Methods have been devised which relate measurement of discontinuity spacings and their distribution along exposures scanlines to RQD for comparison purposes Priest and Hudson 1981 Sen and Kazi 1984 These methods are not pertinent to this exercise but may prove useful to you in any eld rock mass characterization problems you may encounter Drilling operations also may affect RQD percentages for cores RQD was developed for NXsize cores 54 mm dia Smaller diameter cores may break up during drilling resulting in misleading RQD values Breakage may occur during drilling of NX or larger size cores and also when cores are being removed from the core barrel or tted into the core box Weathering at natural breaks often provides a clue as to the kind of break either natural or arti cial Figure 72 shows 33 Engineering Geology a Laboratory Manual natural breaks with discoloration from weathering If the breaks appear to be fresh unweathered and clean arti cial breakage can usually be assumed Such pieces should be tted together with the total length of assembled core recorded for RQD use If in doubt as to the natural or arti cial origin of the breaks a conservative approach is to consider the breaks as natural It is better to err in favor of a conservative RQD percentage References to RQD its uses and shortcomings are numerous in the geotechnical literature gure 72 The following references provide general and speci c information about the subject in addition to the references on page 72 Deere et al 1967 Geological Society 1977 ISRM 1978 USBR 198 Mathewson 1981 Brady and Brown 1985 ASTM 1988 Johnson and DeGraff 1988 Kehew 1988 Bieniawski 1989 Franklin and Dusseault 1989 West 1990 and Goodman 1993 PROBLEMS This exercise provides an opportunity to compare core recovery with RQD The data have been obtained from the core shown in Figure 71 If you have made visual estimates of core recovery and RQD from the gure this exercise will permit you to compare them with actual measurements Given I Total length cored 10 ft I Measurement data in Table 72 Table 72 p CORE MEASUREMENTS I 1 ROW 1 ROW 2 ROW 3 ROW 4 ROW 5 ROW 5 P P COIN M 39 17 22 G7 16 16 Kquot r imw 18 32 16 15 43 3 8 20 20 30 ml 2 ea quot2 11 L 13 dr W1gt q 39ew quotquotquotquot39 r mi 1 9quot 1 mm p it Q EXERCISE 7 Core Loss and RQD 39 Problem 1 Determine core recovery Determine RQD Problem 3 Visually compare calculated values of core recovery and RQD with the core shown in Figure 71 where each box row is 2 ft long QUESTIONS 1 Although fracture spacing can be estimated from RQD values it may not correctly represent the actual spacings in a cored interval Can you think of a case where both core recovery and RQD can be near 100 and yet nd that the rock mass sampled by the core has many discontinuities 2 RQD applies to a given cored interval in our case 10 ft Is it safe to assume that discontinuities are evenly spaced throughout the cored interval Explain 3 Why is it important to know where signi cant core loss has occured in a cored interval 4 How does orientation of a drill hole combine with orientations of rock mass discontinuities to introduce bias into RQD percentages and interpretation of rock mass quality P 5 When describing the geotechnical characteristics of a rock mass in addition to describing the 1 rock and appearance of the discontinuities RQD is only one of several measures made of discontinuities This is because RQD is a relatively poor three dimensional representation of Pi a rock mass To obtain a more complete picture of a rock mass aside from rock types etc s one must obtain oriented cores from the subsurface andor make surface measurements of discontinuities from exposures Think of four 4 characteristics of discontinuities that are not determined from RQD measurements alone APPLICATIONS Drilling and especially coring are necessary parts of subsurface exploration at most engineering construction sites When cores are obtained the presence of core loss and its relation to RQD u E Q a Total all piece measurements in Table 72 1 J3 J W 1 7 b Divide total by length of cored interval and multiply by 100 73 E 1 0 D E Problem 2 a Total all piece measurements 2 4 in 9 Pk w b Divide this total by the length of cored interval and ultiply by 100 p n 1 3 p n 3 p n 9 Ere 39 40 Engineering Geology a Laboratory Manual are the first indicators of potential design and construction problems related to the site Core loss and RQD must be combined with the following careful examination and description of rock types encountered relation of core loss zones to rock types and discontinuities weathering discontinuity spacings within the core and descriptions of discontinuities Description of discontinuities should cover freshness of the break roughness lling materials and orientation All of these factors must be pieced together in order to provide rock mass quality indicators which are of much greater value than a simple core description Careful field examination of rock exposures and geomorphic features should be combined with the core data and any data gathered from prior geologic or geotechnical work in the area before planning a drilling and coring program The number of holes drilled may be limited and they should be located and drilled to depths which will provide the greatest amount of useful information LOOKING AHEAD The discontinuities seen in cores are of great importance in determining stability of roof and wall rock in underground construction and in surface cuts which expose a rock mass The orientation of the various discontinuities in a rock mass is the subject of the next exercise In Exercise 9 the influence of discontinuities on rock mass stability will be examined References Cited ASTM 1988 Rock classi cation ystems for eigzineering ptgposes Am Soc Test Mater STP 984 167 pgs Bieniawski Z T 1989 Epgineermg rock mass classi cations John Wiley amp Sons Inc 251 pgs Brady B H G and E T Brown 1985 Rock mechanics for underground mining Allen amp Unwin 527 pgs Deere D U Hendron A J Jr Patton F D and Cording E J 1967 Design of surface and near surface construction in rock Proc 8th Symp Rock Mech Am Inst Min Metall amp Pet Eng Minneapolis Minn pp 237302 Franklin J A and M B Dusseault 1989 Rock engineering McGrawHill Book Co 600 pgs Geological Society 1977 The descmition of rock masses for engineering pupposes Geol Soc London Eng Group Working Party Q J Eng Geol Vol 10 pp 355388 Goodman R E 1993 Engineering geology rock in engineering construction John Wiley amp Sons 412 pgs ISRM 1978 Suggested methods for tlgciuantitative description of discontinuities in rock masses Intl Soc Rock Mech Comm on Standardization of Laboratory and Field Tests Intl J Rock Mech Min Sci amp Geomech Abstr vol 15 pp 319368 Johnson R B and J V DeGraff 1988 Principles ofEngineering Geology John Wiley amp Sons 497 pgs Kehew A E 1988 General geology for engineers Prentice Hall 447 pgs Mathewson C C 1981 Engineering geology Charles E Merrill Pub Co 410 pgs EXERCISE 7 Core Loss and RQD 41 Priest S D and J A Hudson 1981 Estimation of discontinuity spacingand trace length using scanline surveys Int J Rock Mech Min Sci amp Geomech Abstr Vol 18 pp 183197 Sen Z and A Kazi 1984 Discontinuitgspjcingand RQD estimates from finite length scanlines Intl J Rock Mech Min Sci amp Geomech Abstr Vol 21 pp 203212 USBR 198 Engineering ge0logL eld manual U S Bureau of Reclamation 598 pgs West G 1991 The eld description of engineering soils and rocks John Wiley amp Sons 129 pgs EXERCISE 8 73 if A g i y cHARAcTERtztggtIG P Z 1 DISCONTINUITY P rTTERNS Y easures of rock mass quality such as core loss and rock quality designation RQD do not provide adequate information about the patterns threedimensional distributions of joints bedding and other planar discontinuities ing a given rock mass Spherical or stereographic projections are widely used when quantiltative descriptions of rock mass discontinuity patterns are required In most geotechnical applications the lower hemisphere of the sphere is used to show planar orientations Two stereanets are used for most applications namely the Wul equalangle net and the Schmidt efual area net The Wulff net also may be referred to as a stereographic net and the Schmt net as a Lambert net Descriptions and uses of these nets and selected references comprise ppendix 2 mM Thealarea net ill be used for this exercise It provides the unique opportunity to observe te h P variations within a given discontinuity orientation or set Both types of stereonet show the relative positions of discontinuities equally well This exercise begins with the case of a given rock mass that has three distinct discontinuity sets Multiple strike and dip readings have been taken on exposures of each set In this example random discontinuities joints in this case are ignored as they are not pervasive through the rock mass It must be emphasized that stereographic plotting of such data does not provide any indication of spacings between individual discontinuities within a given set Thus this important factor in rock mass characterization is lacking However this does not minimize the importance of stereographic plots as being the best means of presenting threedimensional features of a rock mass Figure 81 is a photograph of the site selected for use in this exercise The view is looking east The nearvertical discontinuity set just north of east is foliation in the rock mass The other two discontinuities are joints Two important things are apparent in the photo It can be seen that one joint orientation provides a failure surface along which blocks can move by gravity toward the observer The other joint and foliation orientations complete the formation of blocks that can move on the first joint Thus all three of the discontinuities contribute to the potential hazard of rock falls at this site The second important item involves spacings between adjacent discontinuities of the same set a factor noted earlier Each set in the photograph shows considerable variation in spacings and the resulting sizes of blocks that may slide to Figure 81 42 g EXERCISE 8 Characterizing Discontinuity Patterns 43 ground level Stereo plotting of strikes and dips at this exposure reveals the orientations and related hazards well but it does not display any spacing characteristics which also contribute to the hazard Plotting all of the planes for the strike and dip measurements which characterize the rock mass in Figure 81 serves little purpose We will plot poles to the planes which will be given later for the foliation and each of the two joints Usefulness of poles is at least threefold First the plotting of many planes 74 in our case results in amaze of great circles making interpretation difficult Second the cluster of poles permits determination of the mean average orientation for the given discontinuity set which in turn can be shown by a single great circle or plane on the overlay sheet Third the distribution of poles about the mean gives a measure of variation in orientation of measured planes in a given set If this variability has not been recognized as a systematic structural change in the eld as readings were taken it may then be a measure of the waviness or departure from a planar state along individual discontinuities in a given set Waviness plays a part in rock slope stability which will be investigated later in Exercise 9 The results of the plotting of poles for this exercise are shown in Figure 82 so that at this point you can observe pole orientations for the three sets of discontinuities shown in Figure 81 Figure 82 also provides an opportunity to illustrate a feature provided by the Schmidt equalarea net This is the capability to contour the density of pole distributions on a projected surface on which all pole positions are spatially correct Contouring assists in picking the mean pole orientation of a given discontinuity set and usually is an improvement over the selection of a mean pole as noted above The pole and its orientation may be estimated visually from the contoured poles Access to a computer program which can provide such data directly from the strike and dip data obviously is an N advantage to the user z U Folsotion A Joint J 4 JOINT 392 CONTOUR INTERVAL 5 Contouring of pole densities will not be done in this exercise because of the wide range of geologic training of users of this manual Those who have taken structural geology and have access either to pole counting materials or computer programs may wish to contour the pole densities Figure 83 illustrates the density contouring of the poles generated by data used in this exercise It uses a 5 contour interval Use of contours in obtaining mean poles is evident JOINT 1 JOINT 2 Figure 83 44 Engineering Geology 21 Laboratory Manual Although stereographic projections are the most commonly used methods of depicting discontinuity patterns in geotechnical applications there are other techniques available The cumulative sums technique Piteau and Russell 1972 Piteau 1973 presents strike and dip orientations and concentrations densities in a rectangular grid format This technique is preferred by some workers but it is more time consuming to prepare than stereonet plots and is not as visually useful to most users The rose diagram or polar histogram version of it is used if only azimuthal orientations of discontinuities are required Construction of rose diagrams may be found in many structural geology laboratory manuals PROBLEMS In this exercise orientation data from the three sets of discontinuities described above will be plotted as poles on a stereonet Estimates of the mean orientaions of the sets will be made and compared with their field exposures shown in Figure 81 Given a Orientation data right hand rule Table 81 5 Column in Table 81 for conversion of strike and dip data to polar orientation Stereonets in Appendix 2 K pZ H El ri amp W E Table 81 1 jfx few J ointj lg pf Joint 2 Foliation Strike amppd ip lf91e f Strike amp dip Pole Strike amp dip Pole p 356 5139 260 84 1741662 03 357 51 255 85 151 46 350 43 259 79 165 54 34147 261 81 171 51 342 52 255 81 160 53 351 49 259 82 166 52 347 47 259 81 174 45 341 58 260 83 169 50 342 49 262 80 171 54 346 53 260 82 171 53 344 53 261 83 164 56 350 53 260 84 165 55 170 57 171 53 163 60 169 53 163 61 166 43 160 45 169 48 154 48 161 48 166 60 160 54 EXERCISE 8 Characterizing Discontinuity Patterns 351 53 351 51 351 56 345 55 351 55 351 54 348 56 350 54 351 56 349 52 350 53 355 54 350 54 45 If you have not used stereonets or are in need of a review please go to Appendix 2 The instructions and exercises for plotting planes and poles are designed to prepare you for this exercise Plot poles for joint 1 joint 2 and foliation a Convert strike and dip data to pole orientations and enter in Table 81 b Plot each set of data on a tracing paper overlay placed on the Schmidt equal area net Option 1 Using the overlay sheet with the Schmidt azimuthal net the poles can be plotted directly without rotation of the overlay sheet Option 2 You may plot the poles on an overlay sheet over a Schmidt meridional net If you do so the overlay sheet must be rotated to an east west orientation for each pole that is plotted Though time consuming you may nd that plotting a few poles in this manner will help you to better visualize the relation between planes and poles j i Db39lEilll Determine the mean orientation strike and dip of each discontinuity set a Examine each cluster of poles on the overlay sheet and mark your estimate of the center of each cluster The three poles you select should lie in positions similar to the centers of the contoured areas on Figure 83 46 Engineering Geology a Laboratory Manual b Place the overlay sheet on either the azimuthal or meridional net used above and determine the orientation of each of the estimated mean poles c On the same overlay sheet construct great circles for each of the poles using the meridional net Label each discontinuity set lttT1Pquot bl m3 Examine the angular differences between adjoining discontinuities a Note the near orthogonal 900 pattern formed by the intersection of the joints and foliation This can be confirmed by examining your pole plots mean pole plots and planes representing the poles b Angles can be measured by placing the overlay sheet over the meridional net and counting off the degrees between the strikes or dips of the adjoining planes 0S Problem Compare the discontinuity orientations obtained above with the view of the site in Figure 81 a It is important to relate the eld expressions of discontinuities with both pole plots and plots of planes representative of the pole clusters Do you agree with the statement on page 8 1 that the view in Figure 81 is to the east If not why E b Which joint 1 or 2 is inclined toward you in the photograph Wyn 3quot M Pr0j bl m jgt 5 R Exainine the distribution of each set of poles a With the overlay sheet the differences in orientation within each discontinuity set are seen more easily than in the smaller Figure 82 The greatest variation occurs in measurements made on joint 1 Some indication of this can been seen in the limited 8 F view of the site shown in Figure 81 4quotquotquotquotquotquotquotquot w Q UES rrozvs 1 Of the three discontinuities at the site shown in Figure 81 which one is visibly the most continuous 2 On which discontinuity does sliding of rock blocks occur as the other two discontinuities complete the development of the rock blocks 3 Do the combined orientations of these discontinuities present potential hazards when they are exposed by natural processes or construction Why 4 Examine Figure 81 and give at least two rock mass characteristics in addition to orientation that contribute to the potential for rock fall hazards at this site EXERCISE 3 Characterizing Discontinuity Patterns 47 APPLI CA TI ON S Collection and giquota 1sircal presentation of discontinuity orientation data of a rock mass at a site prior to project design and construction are of critical importance Many lives and considerable sums of money have been lost because of the lack of or proper use of such data The questions above deal with the importance of the interaction of multiple sets of discontinuities Differing numbers and orientations of discontinuities at sites cause a variety of rock block shapes which can be obtained from stereonet examination The presence of a simple inclined surface of sliding at the site chosen for this exercise is quite common At other sites the intersection of two discontinuities may form wedge shaped blocks which can slide into an excavation or fall from the roof of a tunnel Discontinuity sets characterized by their persistence continuity normally are of greatest interest However most sites have less persistent discontinuities typically joints which will be evident on pole plots These may be identified in some cases by the presence of scattered poles on the net overlay which may have crude clustering if any However as continuity is not shown by stereonet plots one should rely on good field notes to determine which discontinuity sets are of importance at a site The mean orientations of multiple sets of discontinuities are used to assess for example the stability of slopes along a proposed road cut alignment and roof fall hazards in tunnels All modern rock mass classi cations used for design of tunnels open pit mines and rock cuts utilize discontinuity orientation data The presentation of such data in the graphic form provided by stereonets along with the potential of estimating variability within each discontinuity set are added benefits derived from this application of stereonets LOOKING AHEAD The subject of rock fall hazards resulting from intersecting discontinuities has been pervasive throughout this exercise In Exercise 9 stereonets will be used again to examine the potential for slope failures controlled by discontinuities in rock masses Natural processes and construction practice may contribute to failure potential as noted in this exercise References Cited Piteau D R and L Russell 1972 Cumulative sums technique A new approach to analyzing joints in rock Proc 13th Symp on Rock Mechanics Am Soc Civ Eng Urbana Ill pp 129 Piteau D R 1973 Characterizing and extrapolating rock joint properties in engineering practiceRock Mech Supp 2 pp 131 Also see references in Appendix 2 EXERCISE 9 i ROCK SLOPE STABILITY E tablity of slopes in rock masses is controlled with few exceptions by discontinuities A number of factors relating to discontinuities are involved The most important factor is orientation Other factors are the number of discontinuity sets the spacings within discontinuity sets and irregularities such as waviness on potential failure surfaces All were introduced in Exercise 8 In this exercise we will examine how these factors are specifically related to slope failure Stereonets provide an excellent means of analyzing the potential for slope failure from the standpoint of possible movement without considering the forces acting on a sliding mass This kind of analysis is called a kinematic analysis Forces involved in rock slope failure constitute another area of slope failure analysis that usually is in the domain of rock mechanics rather than engineering geology The type of analysis we will make in this exercise is not a true kinematic analysis because we will be introducing friction which is a force that restricts downward movement We will not be considering gravitational forces which must overcome the frictional resistance to movement It is this more complete analysis which is in the domain of rock mechanics Determination of whether a slope can fail primarily depends upon whether a potential failure surface is or will be exposed at a site This involves the introduction of natural and construction slopes into the stereonet analysis The slope aspect and amount both are critical factors in analyzing potential failure Slope aspect is the direction a slope faces The amount is the slope angle from the horizontal and is analgous to dip Thus if the aspect of a slope natural or manmade is the same as the dip of a discontinuity set at a site failure along one or more surfaces in that set might be expected if the angle of slope is greater than the dip angle of the given discontinuity set In such cases the discontinuity set is said to O Figure 81 in Exercise 8 reproduced here as Figure 91 shows a rock face exposed by an old road cut The exposed surfaces of joint 1 see Exercise 8 dip toward the viewer at an angle less than the slope of the road cut As a result joint by the road cut Sliding of rocks by the two joints and the foliation has occurred on jointl since the road cut was constructed Joint 2 and the foliation do not daylight as no potential sliding surface is formed by either one with the given cutslope orientation Figure 9391 48 as V 5 339 39 751 Q6quot quot J EXERCISE 9 Rock Slope Stability 49 Figure 92 provides an opportunity to view another daylighted joint set from a different angle than that seen in Figure 91 In keeping with the de nition of daylighting the joints dip at an angle less than that of the cut slope which in this case is a quarry face Minor downslope displacements have taken place along several of the daylighted surfaces Slopes can be shown on stereonet projections of a site They appear as planes great circles having orientations the same as the slope aspects and angles occurring in the eld Comparison of the strike and dip of a cut slope with that of a dipping discontinuity can be made directly on the projection Figure 93 is the stereonet projection of the Figure 91 site showing the discontinuity planes The road cut orientation has been placed on the figure It has an orientation of N 50 W 700 SW The azimuth direction of the cut slope roughly parallels the strike of joint 1 The daylighting of joint 1 is shown on Figure 93 by the cut slope angle being greater than the mean Figure 92 dip of the joint A comparison of the planes shown on Figure 93 with those that you plotted in Exercise 8 will show different positions for the planes The Wulff or equal V angle net has been used here and will be exercise instead of the Schmidt equa1 area net In this exercise we are more siope interested in correct representation of Folmon angles than the relative positions of poles as in Exercise 8 As illustrated at the site in Figure 91 single daylighted joint surfaces illustrate a planar type of failure A basic 39 kinematic analysis of sites such as this requires plotting of only the daylighted discontinuity and the natural or constructed slope which causes it to be daylighted Any or all of the daylighted surfaces could slide fail For example in Figure 91 failure has occurred on many of the daylighted surfaces of joint 1 In other cases failure may occur on just one of the surfaces of a discontinuity set Downslope or driving forces generated by the dip of the sliding surface and the the weight of the overlying material are kept from mobilizing to failure by friction along the surfaces as noted earlier Joint 1N15 W 53 sw Joint 2N 12 W 3952 NE FuIiatian N 7905 azonw Cut aIope N 5 w 7osw used for all net constructions in this Figure 93 Friction results from irregularities along discontinuity surfaces These irregularities or roughness consist of large scale waviness Exercise 8 and smaller scale irregularities or asperities on a surface Some refer to the latter as roughness Roughness in its larger sense and its measurement are well documented in the literature and will not be described further here 50 Engineering Geology a Laboratory Manual Barton and Choubey 1977 ISRM 1978 USBR 198 Hoek and Bray 1981 Reeves 1985 Johnson and DeGraff 1988 Franklin and Dessault 1989 Friction along a potential sliding surface is represented by a friction angle which is analagousito the angle of internal friction mobilized at failure of an intact rock Exercise 3 Although a friction angle value for a given surface can be determined in either the lab or eld the cost and uniqueness of test results at a site usually result in the use of a conservative friction angle obtained from published data for a given rock type Reeves 1985 Franklin and Dessault 1989 and Wyllie 1991 The friction angle can be shown as a circle the friction circle on a stereonet construction This is possible because friction can act in all directions on a surface In our case it acts down dip Figure 94 has a friction circle of 35 placed on the stereonet for the Figure 91 site and its stereonet Figure 93 This is a relatively conservative average value for the site It can be seen in the figure that the daylighted dip of joint 1 is greater than the friction angle circle On any surface where the dip angle exceeds the friction angle the slope is unstable An equilibrium state would exist where the two angles are equal and a stable slope would have a dip angle less than the friction angle Just the pertinent portions of the projection are shaded to highlight them in Figure 94 Figure 95 Figure 94 The sliding direction of a potentially unstable slope is down dip ie normal to the strike of the discontinuity In our example it is shown by the arrows in the stereonet figures Any change in the orientation of the cut slope in which the sliding direction lies outside the shaded area will result in a potentially stable slope The shaded area is de ned by the daylighted joint the cut slope and the friction circle In Figure 95 the azimuth of the cut slope has been shifted to N 450 E By doing so the sliding direction falls just at the intersection of the joint and the new cut face At this point the sliding direction arrow is no longer daylighted and the slope can be expected to be just stable Remember from Exercise 8 that our stereonet projections of planes are only mean orientations derived from pole plots of joint sets joint 1 for our case here Thus there will be individual joints within the set which have greater and lesser dips which may affect the stability of the slope In addition spacings of discontinuities within a set are not shown on a stereonet EXERCISE 9 Rock Slope Stability 51 projection of a site Also in addition to the expected variations in roughness within a rock mass prior failure along one or more of the daylighted discontinuities in the past may have resulted in signi cant reductions in the expected friction angles The engineering geologist in the eld must be aware at all times of this possibility and the daylighting of such discontinuities by construction All discontinuities in exposures and cores of the rock mass must be examined carefully before construction begins Daylighting of discontinuities is not limited to construction of road cuts as might be implied to this point Open pit mine excavation and haulage road construction cause daylighting of multiple discontinuities depending on location in the mine Figure 96 shows steeply dipping well de ned planar foliation surfaces which were daylighted by tunnel construction Rock mass failure occured at this site Figure 97 Joint 1H 50 55 SW Joint 2H 5E E 6U N W Cut slopeN 6D W Friction circIa 339P Figure 96 See fooote 1 J P Two discontinuities may intersect in a rock mass to form a wedge shaped block see Appendix 2 If the two E discontinuities and their intersection line 0zJ Q or plunge daylight movement may p occur Wedge shaped blocks are quite common Figure 97 and an analysis of stability is similar to that for planar blocks in that they involve orientations of Figure 98 the discontinuities and the slope natural or arti cial 1 Reprinted by permission of John Wiley amp Sons Inc from PRINCIPLES OF ENGINEERING GEOLOGY by Robert B Johnson and Jerome V DeGraff Copyright 1988 by John Wiley amp Sons Inc 52 Engineering Geology a Laboratory Manual The wedge shaped block used as an exercise in Appendix 2 is reproduced here as Figure 98 using the Wulff net instead of the Schmidt net used in the Appendix The plunge angle and its direction are the basis for determining potential kinematic failure instead of either discontinuity as sliding occurs along the intersection or plunge line Each plane plays a part in potential failure but the wedge will not move if the slope does not daylight the intersection line A cut slope and angle circle of friction have been added to the gure to illustrate daylighting of the line of intersection and the instability of the wedge The portion of the shaded friction circle limited by the cut slope de nes stability or instability In this case the intersection of the planes is at a lower angle than the cut slope daylighted and steeper than the fricton angle unstable As with planar discontinuity failures chance of slope failure is reduced by changing the orientation of the slope azimuth slope angle assuming geologic conditions remain constant If a new cut slope orientation was chosen similar to that in Figure 95 the wedge would become stable and joint 2 would then become unstable This illustrates how important it is to make measurements in the eld of all discontinuities as changed construction design can result in signi cant changes in slope stability at a site Wedges that are asymmetrical about the plunge or intersection line result in one plane of the wedge contributing more to the total frictional component of stabilty than the other Figure 7 illustrates this The friction of the discontinuity in the foreground an old failure surface controlled movement when failure of the wedge occurred along the plunge line during construction of the road cut This exercise involving failure of rock slopes provides an introduction to slope stability Stereonet projections of site conditions can involve pole scatter of each discontinuity involved extensions of pole orientations into the upper net hemisphere and further examination of friction components and contributions of each plane in a potential wedge failure Books by Goodman 1976 1989 Hoek and Bray 1981 Priest 1985 and Wyllie 1991 are recommended if more advanced uses of stereonets are needed for analysis of rock slopes PROBLEMS Stability of planar and wedge shaped rock blocks will be determined in this exercise The influence of construction conditions at a site will be evaluated Given Data for wedge problem I Joint 1 N 600 E 4OONW I Joint 2 N 40 w 46 NE I Cut slope N 87 W 400 NE 0 i Friction angle 45 for each joint Wulff net from Appendix 2 EXERCISE 9 Rock Slope Stability S3 mac V1 W Problem 1 Plot and label all three planar surfaces and the friction circle on a sheet over the Wulff net lgioblem 2 Plot and label the intersection or plunge line and its dip using the method described under quotInte17seic n of planesquot in Appendix 2 Plot and label the pole to each plane and determine the pole to the plane defined by these poles Use procedure steps c f of quotIntersection of planesquot in Appendix 2 QUESTIONS What is the plunge angle of the intersection of the joint planes pB The plunge azimuth and dip defined by using poles to the joints should coincide with the S intersection point on the overlay sheet Does it If not check your constructions L 539l 71 1zi gfV E r p Is the intersection or plunge line daylighted by the cut slope qcgt3 4 Examine the position of the joint intersection and the friction angle circle Is the wedge fw o 9 wl 39 stable or unstable Why nLiw 49gt Assume that a planned transportation corridor through the site area has changed the 09 orientation of the cut slope to N 35 W 60 NE 1 isquot39quot39 g a Is this still a wedge failure problem If not what type is it i b Is the new site potentially stable or unstable i E a acrvr 391 J5 Sr EuS quotquot PO0 J A in P p f c If it is unstable what factors make it so quot5 Lnquot 21 fl T 1 d What is the potential sliding direction if the rock mass is unstable 39 5 s y e How can stability be established if the alignment azimuth of the slope A A cannot be changed APPLI CA T I ONS Analysis of potential slope failure is an essential first step in a complete analysis of rock slope stability In addition to the basic analysis done in this exercise stereonet stability analyses can be greatly enhanced One way is by working with each plane forming a wedge to define better the in uence of the friction angle of each plane on potential failure As noted in the exercise 54 Engineering Geology 21 Laboratory Manual text analysis must be made of forces that cause a slope to fail driving forces and forces that resist failure resisting forces This involves estimation of the weight of overlying materials calculation of its normal component on the sloping failure surface and calculation of the resulting driving and resisting forces from the known or estimated friction angle At that point nal adjustments in construction design including the addition of rock bolts or other types of support must be made before actual contruction can begin Cited and Selected References Barton N and V Choubey 1977 The shear strength of rock joints in theory and practice Rock Mech Vol 10 pp 154 Franklin J A and M B Dussault 1989 Rock engineering McGravvHill 600 pgs Goodman R E 1976 Methods ofngeolggical engineering in discontinuous rocks West Publishing Co 472 pgs 1989 Introduction to rock mechanics 2nd ed John Wiley amp Sons Inc 562 pgs 1993 Engineering geology rock in engineering construction John Wiley amp Sons Inc 412 pgs Hoek E and J Bray 1981 Rock slope engineering rev 3rd ed Inst Min Meta1l London Eng 358 pgs ISRM 1978 Suggested methods for thguantitative description of discontinuities in rock masses Intl Soc Rock Mech Comm on Standardization of Laboratory and Field Tests Intl J Rock Mech Min Sci amp Geomech Abstr Vol 15 pp 319368 Johnson R B and J V DeGraff 1988 Princmjles of engineering geology John Wiley amp Sons Inc 497 pgs Priest S D 1985 Hennjahericamroiection methods in rock mechanics George Allen amp Unwin Ltd 124 pgs Reeves M J 1985 Rock surface roughness and frictional stienngth Intl J Rock Mech Min Sci amp Geomech Abstr Vol 22 pp 429442 USER 198 Engineeg geolngv eld manual U S Bureau of Reclamation 598 pgs Wyllie D C 1991 Foundations on rock E amp FN SPON 333 pgs I 7 1 E 6 39 ix EXERCISE 10 i T in mop ucnon s PHYSICALPRi0PERTIfESs T n the simplest terms soil is what you have if you don t have rock The dif culty in de ning I soil arises from the different views taken by professions dealing with this earth material The view described above represents the engineer s perspective on what de nes a soil It expresses their interest in using earth materials for building or founding structures Soil will behave quite differently from rock for these purposes The soil scientist or agronomist thinks of soil as the material extending from the ground surface to a depth of 1 meter or less that is weathered from underlying bedrock or deposited rock and sediments This view stems from their concem for soi1 s in uence on the plant root zone and biologic activity largely limited to this 1 meter thickness Geologists equate the engineer s view of soil with the regolith Regolith describes any unconsolidated earth material mantling the surface of the earth It could range from a thickness of sediment transported and deposited on solid rock to particles resulting from complete physical or chemical weathering of rock In most instances regolith will include saprolite in situ rock which retains its original texture and coherence despite chemical weathering The engineer and geologist will have no communication problems as long as the geologist recognizes the equivalency of the engineer s soil and the geologist s regolith How a soil responds as a mass is usually the important consideration to both the engineering geologist and the engineer The soil mass is a system consisting of solids air and water This system controls the physical properties of soil and relationships in uencing how a soil mass I I responds to excavation loading or other human activities Solids make quot51 p 39f 395q up most of a soil mass It is usually mineral material Some organic quot739Q4f 52quotquot 3939 material also may be present The space between the individual solid 5 particles is occupied by either air a gasor water a liquid Figure 101 0 shows a cross section of a representative soil mass The different sized IiE393939 G 5 3 solid particles are distributed throughout the cross section The spaces between the solid particles contain air and water If the solid material 5 a 139393939 I z could be segregated to the bottom of the cross section with the water and air stacked on top it would show the proportion of each phase or type of material comprisin g the soil mass This conceptual view representing a soil by its solid water and air components is called a phase diagram Figure 101 55 56 Engineering Geology a Laboratory Manual Figure 102 is a phase diagram labeled with the weight and volume relationships that de ne the soil mass These descriptive characteristics enable the geologist to determine the physical properties of a particular soil The relative amounts of solids air and water determine the unit weight of a soil mass The f Va Air 7 unit weight 7 is calculated with the formula Vvwif I W ii i ir weight of soil mass volume ofsoil mass The unit weight of the soil mass includes the weight of the solids and water The weight of the air present is negligible and can be ignored In contrast the volume includes the space occupied by all three components of the soil mass solids water and air The unit weight for a soil mass consisting of solids Figure 102 water and air is termed the moist unit weight Tm By changing the formula for unit weight to represent the components present in a moist soil mass we can better understand moist unit weight 7 The total weight W of the soil mass would be the sum of the weight of solids Wm and weight of water W This would be divided by the total volume V which is the volume of solids V and volume of voids V g v w lg ig t W Wm W i Y 39 39 39 39quot V Vquot V K Mama Unit weight is a representation of the soil density A soil with a certain weight due to the solids and water which has a larger volume than another soil with the same weight will have a lower soil density This lower soil density will be represented by a smaller moist unit weight than the second soil i 39 The unit weight of water 7 is a constant At 4 C one cubic foot of water weighs 624 pounds Therefore the unit weight of water in English units is 624 lbfta In cgs units the unit weight of water is 1000 kgm3 and 9807 kNm3 in SI units i If the soil mass consisted of solids and water occupying all the voids the unit weight would be calculated with the weight of solids and weight of water divided by the volume of solids and the volume of water This would be the saturated unit weight of the soil 7 39f g E E Y W quot Wquot SCI 2 Vm V p p P EXERCISE 10 Introduction to Physical Properties of Soils 57 If the soil mass consisted of solids with no water present the unit weight would be based on the weight of solids divided by the volume of solids and volume of voids This would be the case for an oven dried laboratory sample The unit weight calculated would be termed the dry unit weight yd V f P 3 7 2 ct iag Ii Wm E i s 5 5 M 39 Yd T i W E 50 9 L 4 g 391 K gig it quot quot J 6 4 0S 39 E ii esquot P P PROBLEMS 0A its Given E I 05 ft3 soil sample Problem 1 Calculate the moist unit weight 7m of this sample Taken from the eld the sample contains solids water and air and weights 593 lbs il f Problem 2 Ia Determine the saturated unit weigh 75 of a fully saturated sample The solid particles weigh 468 lbs The total sample volume remains the same as given for Problem 1 While the weight of water in the sample is not provided it is known that the volume of water in the sample is 012 ft3 Problem 3 Calculate the dry unit weight of the sample yd after oven drying After drying the sample weight is 468 lbs and contains only air and solid particles Problem 4 Convert the answers to problems 13 to S 1 units Note that the answers retain the elements of weight divided by volume APPLI CA T I ON S Representing a soil mass by its solid gaseous and liquid phases engineering characteristics of a soil Variables for which you may not have measurements can sometimes be calculated by using the phase diagram relationships and other available variables For example the saturated unit weight of soil can be calculated from an alternative formula using speci c weight of soil solids unit weight of water void ratio Exercise 13 58 Engineering Geology a Laboratory Manual Unit weight of soil is an important variable in calculations of shear strength and other estimations of soil suitability for engineering purposes Many times it is the inplace unit weight of soil which is of interest The problems of collecting undisturbed soil samplesfor testing and of relating the laboratory results of disturbed soil samples are always a source of concern The unit weight of soil is a variable in some common laboratory tests to determine soil suitability For example the Proctor maximum dry density test Exercise 13 shows the most desirable conditions of an arti cially compacted soil which can be practically obtained LOOKING AHEAD Look at the phase diagram in Figure 102 The only part of the soil mass which can readily change volume is the volume of voids which is the volume of air and volume of water present As long as the soil structure or arrangement of solid particles remains the same the volume of voids will remain unchanged However it is important to recognize that natural forces such as ground shaking during an earthquake or arti cial force such as a mechanical compactor can reorient the solid particles and reduce the volume of voids If the water present in the soil mass remains the same the total weight will remain the same as before volume reduction The same total weight in less volume means the unit weight of the soil mass will be greater re ecting the higher soil density The practical aspects of density changes will be examined in more detail in Exercise 13 Soil Compressibility Useful References BowlesJ E 1979 Physical and geotechnical properties of soils McGrawHill Book Co 478 pgs Hough B K 1969 Basic soils engineering 2nd ed Ronald Press 634 pgs Johnson R B and J V DeGraff 1988 Principles of engineering geology John Wiley amp Sons 497 pgs NAVFAC 1982 Design manual soil mechanics US Dept of Defense NAVFAC DM71 Dept of the Navy 360 pgs EXERCISE 11 SOIL CLASSIFICAETIONA oil is composed of individual particles with differing sizes shapes and mineral composition The engineering properties of soil depend on how these individual particles behave as a mass For engineering purposes it is useful to anticipate the behavior of a soil mass based on its soil classi cation Engineering classi cations of soil typically are based on texture and plasticity The Uni ed Soil Classi cation system is one of the most widely applied soil classi cations for engineering purposes It employs gradation which describes the particles present and measures of how those particles may or may not deform under stress Gradation is a common means for describing the particle size distribution present in a soil This simple soil descriptor is the size frequency distribution of the particles present Gradation characterizes the distribution of particles sizes in a particular soil and any predominance of either fine or coarse particles Particle size terminology differs between engineering and traditional geology This difference is a potential source of miscommunication between the engineering geologist and the engineer Particles which in engineering terminology are called gravel are roughly equivalent to pebbles in geologic terminology There are also differences in the size ranges de ning terms applied to describe different sized particles Engineering terminology de nes gravel as being between 762 mm and 475 mm in size The geologic equivalent pebbles are defined as being between 64 mm and 2 mm in size Sand as defined for engineering ranges from 475 mm to 0074 mm Geology considers sand to be in the size range from 2 mm to 0062 mm Any particle size smaller than 0074 is considered a fine in engineering termsIt can be subdivided into silt and clay Silt would range in size from 0074 mm to 0005 mm Clay would be any particle smaller than 0005 mm In geology the fine fraction is always subdivided into silt and clay size classes Silt has a size range from 0062 mm to 0004 mm Clay particles are smaller than 0004 mm Most sieve analysis forms employ the size ranges and terminology used in engineering Sieve analysis in the laboratory is the standard means for determining gradation Sieve analysis is applied to the soil fraction consisting of gravel sand silt and clay particles If the soil mass contains particles which are cobble or boulder size this information is noted during sample collection Particles this large are not collected for sieve analysis The initial step is to sieve a dry weighed sample of soil The amount of soil retained at each standard size sieve in the stack is divided by the total weight of the sample to calculate the percent of the soil sample retained at each critical size difference represented by individual sieves These percentages are converted to represent the cumulative percent of the sample finer than the size represented by a particular 59 60 Engineering Geology 3 Laboratory Manual sieve The ner fraction of the soil may be further separated by hydrometer or pipette analysis To graph the distribution of particles in the sample the percentages are plotted against the sieve sizes and the particle size classes they represent Detailed procedures for sieve analysis are found as US Bureau of Reclamation Designation E6 USBR 1974 and American Society for Testing and Materials ASTM D 42263 ASTM 1990 Another source of mis communication between the engineering geologist and the engineer can arise when describing the gradation of a soil Engineers refer to how a soil is graded to describe the relative proportion of particle sizes present This is similar to the concept of sorting which geologists use in sedimentology The confusion arises because the terms engineers apply to grai 0 39 n posite meanings to those which geologists apply to sorting For example p M raded p fairly equal amounts of particles ranging from large to small This is represented by cu A in Figure 111 To the geologist this would be a poorly sorted material Curve B Figure 111 shows a poorlygraded soil consisting predominately of one size class A sediment consisting of predominately one size class would be described as well sorted by a geologist A skip or gap graa39ed soil is represented by curve C Figure 111 This is a particular type of poorly graded soil with a wider range of large and small size particles present but intermediate sizes being absent The engineering geologist should adopt engineering terminology to facilitate communication with the engineers using the soils information l Notice the curves for the soils in Figure 111 on the next page In contrast to poorlygraded soils which have curves with abrupt changes or steep or very flat curves well graded soils plot as smooth curves across the range of particles sizes For a soil to be truly described as well graded it must also meet certain criteria The coe iciem 0fumf0rm139zy Cu must be greater than 4 for gravel and greater than 6 for sand the coe lcient of curvature Cc must be between 1 and 3 W 1b WWW Mm The fcoef cient of uniformitys calculated from the graph by the following formula 395 kg 5 rquot iii 1 r 9 33 EH W 139 R V R as quot39 w where D60 is the particlesize diameter 0oZ percent of the sample was ner and D10 is the particle size diameter for wh1 h I the sample was ner These same diameters are used in computing the izoef nT6f at W 2 In i 393 D30 U c azgl D10 x D60 W The distribution of particle sizes is the initial criterion used in the Uni ed Soil Classi cation Figure 112 It distinguishes between coarsegrained and nc grained soils based on whether 50 percent or more of the soil passes the No 200 sieve Particles which pass the No 200 sieve will be silt or clay size particles Collectively silt and clay particles are called fines for engineering purposes p p 0Z EXERCISE 11 Soil Classi cation I 51 GRAIN SIZE DISTRIBUTION FINES I SANDS I GFIAVELS 100 Soi A SoI B SoiI C C C 39J C O C h C Percent finer by weight 3 01 C C PO C C I o 001 01 1 1 10 100 Grain size in millimeters Figure 111 The reason for distinguishing between coarsegrained and ne grained soils is their differing response to being wet or dry Soils which consist of particles that stick together in either a dry or wet state display cohesion Cohesion is an interparticle attraction that is dependent on the partic1e size distribution of the soil It is present when the soil has a signi cant proportion of negrained particles The negrained particles are attracted to each other even when dry I Cohesion is especially characteristic of negrained soils with a signi cant amount of clay Fine grained soils are sometimes referred to as cohesive soils 0A Coarsegrained soils lacking a signi cant proportion of negrained particles will stick together when wet but disaggregate into individual grains or small pieces when dry Because coarse grained soils lack cohesion they are referred to as cohesionless or noncohesive soils The importance of distinguishing between cohesive and noncohesive soils for classi cation purposes stems from the need to understand how a soil may or may not deform under stress I Deformation behavior for a particular soil is controlled by the amount of water present With X different water contents a soil may respond in a nonplastic plastic or viscous manner These 1 states describe a soil s consistency Noncohesive soils are nonplastic for almost all ranges of water content A noncohesive soil may deform as a viscous fluid at high water content In P contrast a cohesive soil will change from a nonplastic to a plastic to a viscous state with h increasing water content 62 if UNIFIED SOIL CLASSIFICATION SYSTEM LABORATORY CLASSlFlCATlOl ll CRETERIA Coarse Grained Soils T A GROUP Less than g k SYMBOLS Less than z I x I C33eaterlaz2n 4 GW 5 passing A No 200 t N b th sC d C I b GP GRAVELS sieve size ot meeting 0 C an U va ues a ove Less than of coarse 02 Atterberg llm fraction P belowquotAquot line passes No 4 More than Above quotAquot line with Pl or Pl lt4 sieve size 12 passing between 4 and 7 requires No 200 use of dual symbols sieve size lGCGM Atterberg 39m39 i above quotAquotne u GC K it 0c or Pl gt7 39quot p j s K A i p Mr 4 A W x P P Less than i n 6 gr aterithan wee a nd3 quot SW 5 passingfi p 1 39 SANDS 20 3 We t39 39 b th C d39r quot I b 4 SP More than sieve size R mee ln an quot Va ues a We 12 of coarse A b l f acton er erg um pasges lNO 4 More than Above quotAquot line with Pl below quotAquotline SM sieve size 1235 p2as3ing betweenf4 anld 7 riqlirires use and PI lt4 0 o ua sym os sieve size SCSM A Atterberg hm above quotAquotline SC L and PI gt7 Borderline cases between 5 and 12 require use of dual symbols such axwSC Fine Grained Soils GROUP More than 50 passing No 200 sieve SYMBOLS ML See adjoining plasticity chart CL PAquot linel z SIlTS AND CH CLAYS Below quotAquot line and LL oven dry soil I LL air dry soil lt 075 OL OH Visual identification Pt Figure 112Adapted from NAVFAC 1982 The Arterberg limits provide the means for de ning soil consistency for a cohesive soil They are based on the work of the Swedish soil scientist A Atterberg The Atterberg limits establish the relationship between the water content and the physical state of the soil Figure ll3 illustrates Atterberg limits and water content The solid and semisolid or nonplasric state SL EXERCISE 11 Soil Classification 63 of a soil is de ned by water content ranging from 0 percent to Semi the value when it changes to a Solid Solid Mastic State Liquid plaSt1C state The water content at state state state the point where a soil changes I f Range indicated by rom semisolid to plastic is termed the plasticity index P the plastic limit PL The plastic We 1 LL PL state of a soil is de ned b water SL PL LL content ranging from theyplastic 1 M013tUquote C0 Le L 1quot Cquote051quotl9 limit to the point where it changes 0 from a plastic state to a viscous Figure 1131rOm USER 1974 state This point is termed the liquid limit LL The range of water content de ning when the soil is in a plastic state is the soil s plasticity It is called the plasticity index PI and calculated by E 5 big PI LL PL 1 7 3 ee t gm FOT SO11 classi cation PPTPOSCS PLASTICITE CHART t quot i K plastic index and liquid limit are 50 it L 39 tJ used to form a plasticity chart 50 is I K Figure 114 Soils plotting above 53 Iu e39 Ettff the Aquot line have a very low Q 40 i i permeability and its variation is E CH uni The quotUquot line is E so 99 OH generally accepted as the upper 5 I rah limit of the PILL ratio for soils 3 2 CL Nme c OL 10 Gradation liquid limit and plastic 47 Wt f39L limit define the texture and o W plasticity of a soil A 0 1 2 3 8QUg UM6Tquot 7 8 9 10 textural plasticity classi cation like the Uni ed Soil Classi cation Figure 114 Adapted from NAVFAC 1982 permits a reliable approximation of a soil s suitability for engineering purposes Figure 115 compares some engineering properties such as shear strength and permeability values which are expected for different USC soil types Obviously this level of information is insuf cient for nal project siting detailed characterization or design requirements More detailed analysis of a soil using laboratory testing to evaluate its engineering geologic properties rather than an approximation based on typical soil type behavior will be necessary Assume you have the following laboratory information for a soil 88 percent of the sample passed the No 200 sieve the median grain size is 0005 mm the liquid limit is Q9 and the O plastic limit is 27 The rst step is to classify the soil as coarse or ne grained As noted in Figure 112 thiswis determined by whether more than 50 percent passes or is retained by the No 200 sieve For this soil more than 50 percent passes making it a ne grained soil Another way to look at this criterion is to look at the median grain size If the median grain size which represents the size for which 50 percent of the sample is either larger or smaller is less than 0074 mm equivalent to the No 200 sieve the soil is ne grained The median grain size of the soil is 0005 mm a value less than 0074 mm as expected for a negrained soil 64 plasticity chart On Figure 114 the liquid limit and plastic index for the soil plot line in the domain for either and OH or MH soil type Because the liquid limit is greater than 50 the soil classi es 4 39 snds There are several more steps in classifying sample came from a coarse grained soil the second step would be to classify it as a sand if more than 50 percent of the coarse fraction passed the No 4 sieve or a gravel if less than 50 percent of the coarse fraction passed the No 4 sieve For a coarse grained soil the third step is to classify it as clean or with nes The soil will be a clean sand or gravel if less than 5 percent of the sample passes the No 200 sieve If more than 12 percent passes the No 200 sieve it would be a sand or gravel with nes Intermediate values between 5 and 12 percent would be classi ed with a dual symbol representing both clean and with nes soil types For example a GP GM designation represents a gravel with 10 percent passing the No 200 sieve A fourth step is required to complete classi cation of a coarse grained soil For a clean sand or gravel the coef cient of uniformity and coef cient of curvature should be calculated as discussed earlier Note on Figure 112 the values required for a wellgraded sand and a wellgraded gravel When these values are not met the gravel or sand is classi ed as poorly graded For sand or gravel with nes the fourth step is determining the character of the nes The sand or gravel would classify as having silt nes if the liquid limit and plastic index data plot below the quotA line or the plastic index is less than 4 The nes would classify as clay if the liquid limit and plastic index data plot above the quotAquot line with the plastic index greater than 7 Using Figure 115 on the next page the engineering properties of the example soil classi ed could be approximated as ML This soil would likely have fair shear strength medium to high compressibility fair workability as a construction material and be semi pervious to impervious when compacted The coef cient of permeability k of the soil in place would range from 10 to 10 centimeters per second Field techniques make it possible to eld classify a soil prior to laboratory analysis Explanations of these eld tests are found in many references including USBR 1974 and Johnson and DeGraff 1988 Field testing permits soil samples taken from test pits soil borin gs or surface exposures during eld studies to be classi ed using the Uni ed Soil Classi cation system PROBLEMS Problem I Table 111 following Figure 115 shows the cumulative percentage of ner soil retained at each sieve size for three soil samples Plot each soil on the blank graph provided at the end of this exercise Connect the points with a smooth line using a different symbol for each soil ie dashed solid etc or colors Based on your graph describe the gradation of the three soils and demonstrate that any soil described as wellgraded meets the uniformity and curvature requirements P 1 P aw EXERCISE 11 Soil Classification 65 UNIFIED SOIL CLASSIFICATION SYSTEM mm Permeability Group Typical names Shear Compress Work symbol strength ibility ability When K K compacted cmsec ftday Well graded gravels gravel GW sand mixtures little or no Excellent Negligible Excellent Pervious gt 10 gt 30 nes Poorly graded gravels gravel Very GP sand mixtures little or no Good Negligible Good pervious gt 10 gt 30 nes Silty gravels gravel sandsilt Good to Negligible Good Semiperv 10 3 to 10396 3 to GM mixtures fair to imperv 3 x 10393 GC Clayey gravels gravel sand Good Very low Good Impervious 1039 to 10398 3 x 10393 to clay mixtures 3 x 10 SW Well graded sands gravelly Excellent Negligible Excellent Pervious gt 10 3 gt 3 sands little or no nes SP Poorly graded sands gravelly Good Very low Fair Pervious gt 10393 gt 3 sands little or no nes SM Silty sands sandsilt mixtures Good to Low Fair Semiperv 10 3 to 10 3 to fair to imperv 3 x 10 3 SC Clayey sands sandclay Good to Low Good Impervious 10 to 10 3 x 10393 to mixtures fair 3 x 105 Inorganic silts and very ne ML sands rock our silty or Fair Medium to Fair Semi perv 10 3 to 1039 3 to clayey ne sands with slight high to imperv 3 x 10393 plasticity Inorganic clays of low to CL med plasticity gravelly Fair Medium Good to Impervious 10quot to 1039 3 x 103 to clays sandy silty and lean fair 3 x 10395 clays Inorganic silts micaceous or Fair to Semiperv 3 x 10quot to MH diatomaceous ne sandy or poor High Poor to imperv 10quot to 10 3 x 103 silty soils elastic silts CH Inorganic clays of high Poor High to Poor Impervious 10quot to 10quot 3 x 10393 to plasticity fat clays very high 3 x 10395 OL Organic silts and organic silt Semi perv 3 x 10quot to clays of low plasticity Poor Medium Fair to imperv 10 to 10 3 x 10 3 LL lt 50 OH Organic clays of med to high Poor High Poor Impervious 10 to 1043 10 3 to 10 plasticity LL gt50 Pt Peat and other highly organic Not suitable for construction soils Figure 11 66 Engineering Geology a Laboratory Manual Table 111 CUMULATIVE 39 FINER Sieve size Diameter Soil B or number m 3quot 761 2quot 508 381 250 190 125 95 No 16 118 No 30 060 No 40 042 99 No 60 025 98 No 100 015 95 No 200 0074 82 No 230 0062 55 No 270 0050 30 If you were provided with soil samples in the laboratory use the procedure below to determine their gradations The blank sieve analysis at the end of this exercise can be photocopied and used to plot the data Otherwise use semi log paper as described in the procedure Sieve Analysis dry Procedure P e A Select a sample of soil Remove particles larger than 3 inches 761 mm Visually estimate the proportion of this material to the total mass of the sample k m Spread the soil on a tray and dry in an oven at a temperature between 105 C and 110 C am so Allow the sample to cool to room temperature before continuing with the analysis Before 2 sieving weigh the sample to obtain total weight 3 C Assemble a stack of sieves representing the various sizes from about 25 inches 63 mm to z the No 200 sieve 0074 mm The sieve with the smallest diameter is placed over a catch basin Sieves with progressively larger diameter openings are placed on top Place the soil it sample in the top sieve and cover Set the stack in a mechanical shakerThe shaker should 33 2 E 5 r ERERCISE 11 Soil Classification 67 be agitated for a minimum of 10 minutes If no mechanical shaker is available each sieve should be used one at a time Weigh the material retained on each sieve This should include material lodged in the holes of the sieve Dislodge these particles with a sieve brush onto a clean sheet of paper and add to the material extracted from the sieve Prepare a sheet of paper with four columns The rst column should list the sieve sizes or numbers in descending order beginning with the largest Record the weights of the sample retained at each sieve size in the next column Head the second column quot weight retainedquot Total the column of weights retained at each sieve size It should not differ by more than 1 percent from the original total weight of the sample Using the total sample weight divide the weight of sample retained at each sieve size and convert to percent Record this in a third column headed quot percent retainedquot The fourth column will be headed quotcumulative percentage nerquot These are the values used to plot gradation Subtract the percent retained from the cumulative percent ner value of the previous sieve size Continue this calculation until the cumulative percentage passing ner than the No 200 sieve is determined F Plot the cumulative percentage ner values obtained by this analysis against their respective soil sizes on semilog paper The sieve sizes would be arranged on the normal scale and grain size in millimeters on the log scale The log scale will range from 1000 mm to 0001 mm Or use a prepared grain size distribution graph to display the gradation of the soil sample Problem 2 Using the information provided on the next page in Table 112 classify each soil according to the Uni ed Soil Classi cation system Refer to Figure 112 to interpret the data Once each soil is classi ed use Figure 114 to answer the following questions a If these soils were present where an earthen dam was under construction which ones would be unworkable as construction material in the dam access roads or other structures b Which soils would be suf ciently workable as a construction material and capable of being compacted to form an impervious barrier for use in constructing a sanitary land ll quot T 5 r V c If you were evaluating a home site where a high cutslope must be excavated which soils would cause you to have the gr about slope failure because of its shear strength g39f F quot d A buried underground tank is discovered to be leaking A well serving a municipal T water system is located 300 feet away from the leaking tank Based on the coef cient of permeability which of the soil types would you hope was not present at the site If that soil type was present and you knew the leak started 60 days ago what is your estimate of the maximum time left for preventing the leak from reaching the well it 3 we gs 7 68 Engineering Geology a Laboratory Manual Table ll2 Soil I I Passing Passing No 200 No 4 l W 88 100 X as L 100 J Y 4 47 I 012 108 90 NP NP Z 24 76 0005 015 y 150 28 ll rig U50 3901 D2 33925 30 19 QUESTIONS 1 What property of soils is dependant on the presence of a signi cant proportion of ne grained particles 2 Identify the two characteristics which are typically used in engineering classi cations of soil 3 Soils may be referred to as negrained and coarse grained What are the alternative terms which might be used to distinguish ne grained and coarsegrained soils 4 Name the two terminology differences in describing soil which may lead to mis communication between the engineering geologist and the engineer 5 What are the four physical states de ned by the Atterberg limits APPLI CA T I ONS A standard classi cation scheme such as the Uni ed Soil Classi cation permits useful approximations of soil characteristics based on measurement of a few key physical factors This is especially useful for eld evaluation of soils present at a project site or observed in subsurface sampling It also provides a common framework for communicating about different soils and for relating expected behavior such as frost heave potential or shrink andswell potential Gradation can be used to help de ne other aspects of soils than their classi cation The potential for soil piping the removal of ne grained particles by groundwater flow which may create cavities within a soil mass can be related to gradation For this reason the design of subsurface drains requires gradation data to ensure the material used in constructing the drain will not result in soil piping in adjacent soil or become clogged by ne grained particles 0 EXERCISE 11 Soil Classification 69 LOOKING AHEAD The importance of distinguishing between ne grained and coarse grained soils will become more apparent when considering the problems of consolidation and compaction in Exercise 13 The difference in slope stability attributable to this distinction will be evident in Exercise 16 Cited and Suggested References ASTM 1990 Method for particlesize analysis of soils Am Soc Test Mater Ann Book of ASTM Standards Sec 4 Vol 0408 ASTM Designation D 42263 Bell F G 1992 Engineering properties of soils and rocks Butterworth Heinemann 345 pgs Dietrich R V J T Dutro Jr and R M Foose 1965 AGI data sheets for geology in the eld laboratory and office American Geol Inst IIoltz R D and W D Kovacs 1981 An introduction to geotechnical engineerigg PrenticeHall Inc 733 pgs Johnson R B and J V DeGraff 1988 Principles of engineering geology John Wiley amp Sons 497 pgs NAVFAC 1982 Design manual soil mechanics US Depart of Defense NAVFAC DM 71 Dept of the Navy Washington DC 360 pgs Prokopovich NP 1984 Use of agricultural soil sur z maps for engineering geology mapping Bull Assoc Eng Geol Vol 21 pp 437447 USBR 1974 Earth mgnual 2nd ed US Bureau of Reclamation 810 pgs USBR 198 Engineering geology eld manual U S Bureau of Reclamation 598 pgs 70 Engineering Geology a Laboratory Manual GRAIN SIZE DISTRIBUTION GRAPH FINES I SANDS I GRAVELS 100 90 80 70 60 50 40 30 Percent finer by weight 20 10 0001 0010 0100 1000 10000 100000 Grain size in millimeters EXERCISE 12 SOIL MOISTURE he presence of water in soil influences many engineering characteristics The importance of water as part of the soil system is illustrated by the phase diagrams in Exercise 10 Under some circumstances knowing the proportion of the total space in the soil which is occupied by water forecasts the soil behavior In other circumstances it is more useful to know the relative weight of water within the soil Determining the volume and weight relationships of water in a soil is necessary to understanding how the soil mass will behave Water helps define a fundamental physical relationship of soil speci c gravity Speci c gravity GS enables the weight of soil components to be used in determining soil properties normally derived from volume relationships It is derived from the formula G 2 weight of unit volume weight of unit volume of water at 4 C If it is assumed the unit volumeisone cubic meter the formula would be H G weigh of 1 m3 of soil s39 J P pR 5 liem p p quot39 meg The unit weight of water at 4 C is a C stant In metric units it is 1 gram per cubic ramp r In English units of measure a cubic f ot of water at this temperature weighs 624 ounds Using the above formula the speci equotgravity of any solid is the weight of a cubi meter of th39 material divided by 1 Note that speci c gravity is a dimensionless number The principal volume relationship of water in soil is the degree of saturation S Degree of saturation defines the proportion of total space in a soil which contains water It is determined using the formula where Vw is the volume of water V is the volume of voids or space in the soil 71 72 Engineering Geology a Laboratory Manual If the volume of water and volume of voids are equal the soil is saturated The soil mass consists entirely of solids and water This degree of saturation would exist in soil on a river floodplain after oodwater had subsided The other end of this range is represented when there is no volume of water representing an unsaturated condition The degree of saturation is zero This condition is uncommon in nature because some water tends to coat individual soil grains The force of surface tension keeps this water present normally An unsaturated condition would result from oven drying a soil as is done in some laboratory procedures As noted earlier speci c gravity permits volume relationships to be determined from weight measurements The volume relationship of degree of saturation can be calculated using speci c gravity by the following formula S W GS R ea 392 39 6 t 7 J where W is water content G is specific gravity of the soil solids e is the void ratio Void ratio is a representation of the volume of space compared to the volume of solids in a soil mass It is discussed in more detail in Exercise 13 Water content W is the weight relationship of water in a soil mass It is expressed in percent Water content expresses the relation between the weight of water WW and the weight of solids W It is calculated by W W 3x100 W S As shown in the discussion of degree of saturation water content can be used to determine this other variable Laboratory testing determines the optimum water content associated with compaction of a particular soil A detailed discussion of water content and compaction is found in Exercise 13 In Exercise 11 it was noted that negrained soils behave differently with increasing water content For this reason the Atterberg limits were defined by water content PROBLEMS Problem 1 Calculate the degree of saturation for a soil which was determined to have a volume of water of 186 cm3 and a volume of voids equal to 4035 cm3 Problem 2 A 1972 g soil sample is placed in 1000 cm3 container and oven dried in the laboratory After drying it is found to weigh only 1743 g What is its water content ad RQ EXERCISE 1 Soil Moisture 73 Problem 3 Another laboratory sample in a 1000 cm3 container is oven dried After drying it is found to weigh 1676 g The difference between this weight and the wet weight is 241 g It is known from other testing that this soil has a specific gravity of 265 and a void ratio of 058 What is its degree of saturation APPLI CA T I ONS Knowing the amount of water in a soil is useful beyond simply being able to quantify that value For one thing it permits the use of alternative formulas to calculate various unit weights or other soil variables The amount of water in a soil in uences soil mass behavior when stress is applied A load normal stress pressing down on solid material will cause it to compress A simple example is the footprint left when you walk across a dry sand on a beach Your weight ie load caused the sand grains to re arrange into a more compact arrangement with less space between individual grains The result is a depression compared to the surrounding area which maintains the looser less compact arrangement of sand grains and spaces In contrast walking on the sand near the water s edge will leave barely an impression Here the spaces between sand grains are lled with water It is a saturated soil mass The load represented by your foot pressing on the sand surface tries to compress both sand and water The load which the sand alone cannot support is transferred to the water Because the water is confined under your foot and generally confined by the water in the surrounding soil it successfully holds the surface up compared to the area surrounding your foot The force of the water resisting the applied load from your foot is called hydrostatic pressure You may note your foot can create a small depression in the sand surface This will occur where water drains from under your foot into surrounding soil You may observe a sheen of water on the beach surface around your foot as you step down which disappears as you lift your foot This is water draining upward through the surrounding sand to make room for water draining laterally away from under the load created by your foot The sheen disappears as water percolates back into the beach when your foot is removed having reduced the load on the underlying sand and water Hydrostatic pressure decreases as the water initially present in the soil drains This causes some of the load borne by the water to be transferred back to the sand grains which compress into a slightly more compact arrangement Hydrostatic pressure results from the static presence of water in the soil If wells were installed in the sand in a line placed across the beach to the water s edge and beyond the level of water found in each well would coincide with the surface elevation of the water This shows that the energy level or pore water pressure in the sand is the same at every point that the water is motionless within the soil mass Knowing the amount of water present in a soil is an important factor in understanding its behavior It is also important to know the degree to which the water will move within the soil mass The transmission of water through the voids in a soil is a soil property commonly referred to as permeability A soil mass with little or no water transmitting capability would be an impermeable soil 71 Engineering Geo1ogv 3 Laboratory Manual A better term for water transm1tting Hydraulic Conductivity capability 1S hydrauhc c0nductzvity ofselected Soils Hydraulic conductivity k IS the quantity cm 1 SM mm of water which moves through soil or S T SAN rock in a unit of time Heath 1982 539 Some groundwater calculations involving E quot0 the movement of water through soil or TM quotquot39 quot39m rock use the more common term permeablllty rather than hydrauhc 101 1039 10 15 10 mi 10 ml i ii 101 ml I01 0quot conductivity The formulas usually represent water movement as k regardless of the term applied Figure 121 shows hydraulic conductivity ranges for several soils Figure 121 adapted from Heath 1982 The hydraulic conductivity of a soil mass may not be the same in all directions When the hydraulic gradient differs depending on the direction with the soil mass it is referred to an anisotropic condition The soil mass would be isotropic when the hydraulic conductivity is the same in all directions LOOKING AHEAD The importance of hydrostatic pressure will be discussed in more detail in Exercise 13 Change in hydrostatic pressure is a controlling factor for the rate of settlement for compressible soils Exercise 14 addresses the measurement of hydrostatic pressure and the analysis of seepage Hydraulic conductivity also will be considered when examining seepage and drainage of soils in Exercise 14 This material will serve as the basis for understanding how moving water can influence soil strength Cited and Suggested References Heath H R 1989 Basic groundwater hydrology U S Geol Surv WaterSupply Paper 2220 84 pgs Johnson R B and J V DeGraff 1988 Principles of engineering geolggyz John Wiley amp Sons Inc 497 pgs EXERCISE 13 SOIL COMPRESSIBILITY decrease in volume may occur in a soil mass when stress is applied The stress or load compresses the soil mass The load may be static or dynamic A static external load might be expected in the soil under the foundation of a new building A dy7iEzr7fic load might result from mechanical vibrators or ground shaking during an earthquake This engineering property of soils is called compressibility The decrease in volume due to loading results mostly from a change in the volume of voids or space in p It results in a vertical decrease of the top of the soil mass which is referred to as ctttWhen settlement is anticipated the change in soil volume causes no problem or may n besired Problems arise from not anticipating the amount or time necessary for this volume change to take place As discussed in Exercise 10 a soil mass can be viewed as a system composed of solids liquids water and gases air The space occupied by water and air is the volume of voids There are two common measures of this space namely porosity and void ratio Porosity n is the relation of the volume of space to the total volume It is expressed as the proportion of the total volume VL of the soil mass occupied by voids Vv It is typically expressed as a percentage value Use the following formula to determine the porosity for a specific soil mass n 3 x 100 if Emil t The values for porosity will range from 0 lti n T l In other words where there is no volume of voids in the soil mass porosity is 0 This condition is unlikely to occur Equally unlikely is having a soil mass without a volume of so1idis cgmprising part of the total volume Therefore porosity can only approach the value of 1 Because porosity involves the total volume of a soil it is possible to calculate it using relationships which relate weight to volume If the dry unit weight of the soil mass 7 and the speci c gravity Gs of the solids are known porosity n can be calculated by o quotMa i it 76 Engineering Geology a Laboratory Manual Ulfk 4 The unit weight of water 39y is commonly expressed in the English units of pounds per bic foot lbft3 For calculations employing metric units this value would be 1 gramcubic W gm rm K ximl 1 Iquot5 Wl Void ratio e is the relation of the volume of space to the remaining volume in the soil mass the volume of solids V5 The volume of space is again expressed as the volume of voids V Void ratio can range from O to in nity Like porosity it can only approach 0 as the volume of voids becomes nearly the total volume of a soil mass As the volume of voids decreases the void ratio will be constrained only by the value for the volume of solids While it is unlikely in real terms the upper value for void ratio is correctly represented as in nity Just as porosity can be expressed using weight values in place of volume values void ratio can be calculated by 4 Y1 GS 1 Y4 lg E r s Nus 44 Because porosity n and void ratio e involve representation of the space in a soil volume and are calculated using some of the same variables each can be expressed using the other These expressions are as follows e Porosity and void ratio vary with the gradation of soils The differences in the volumes of space found in coarsegrained and f1ne grained soils result in differences in their compressibility With both coarse and f1ne grained soils compression of the soil can result in a lowering of the ground surface or settlement Unless settlement is anticipated and planned for in the design of a structure it can cause serious problems during and after construction The settlement experienced in coarsegrained soils is primarily from compression of the soil particles For the same coarsegrained soil there is a greater volume of voids in a loose soil than in a dense soil Tables in Hough 1969 and NAVFAC 1982 provide some representative soils for comparing these factors If the particles are loosely arranged the settlement occurs as the load stress packs them closer together In some instances fracturing of particles may contribute to the total settlement experienced Generally settlement in coarsegrained soils occurs quickly The settlement in f1ne grained soils results from the drainage of water from the voids Figure 131 on the next page shows conditions before loading with a compressible layer sandwiched quot X quott EXERCISE 13 Soil Compressibility 77 between two more permeable or pervious layers The stress from the initial load placedmoii ea VH1 H H50 1 vs t a fine grained soil 1S borne by p z s 391 FE39MOUS391NCOMPRES SIIBLE S IRATUM393939 b tItie591I12 1Lt1 1 33 andmthe cownrnous BEFORE LOADING 0 water within the voids A quot We D Becau se waterisEEE an IWLLI I I Ii LI t HYDROSTATIC U0 HYDRDSTATIC Excess incompressible material it EXCESS 1 1 Uri we r quot quotquotquotquotquotquotquotquotquotquotquotquotquotquotquotquotquotquotquotquot 39 COLUMNS ARE PIEZOMETRIC tends to Support much of the HEAD IN coMPREssIaLE STRATUM initial load As explained in Exercise 12 the resistance by water when force is applied to L L L L J L J i CONDITIONS DURING LOADING partially or fully saturated soil i PM PRESSURE is called hydrostatic pressure 3 JTLH sq EEE EEEEEN EEEVE Note the hydrostatic excess in V Figure 131 when the load is couomorvs AFTER LOADING applied The resisting force attributable to hydrostatic Figure 131 After NAVFAC 1982 pressure forms an upward arc As water drains from the finegrained soil mass the load is transferred to the soil particles This produces nal hydrostatic pressures limited to the water level in the overlying incompressible layer The phase diagrams in Figure 131 illustrate the change in void ratio e responsible for the settlement or decreased height associated with the reduced water level in the soil mass The lower permeability of ne grained soils means a significant time may pass before drainage is completed Therefore the resulting settlement can occur well after the application of the load This time span can range from days to years A special term consolidation is applied to denote this behavior of fine grained soils under a static load Detwermining the settlement from consolidation and the time rate over which it occurs are important aspects of engineering projects involving finegrained soils To determine settlement from consolidation laboratory testing of the soil is completed to find the ession index E The compression index is a dimensionless number describing the 52 relatio 0 E 0 the void ratio for the expected loadsed in the csdation test Recompmoncuwe 3 the mr to testing lpo and the applied 39 quot quot quotquot39 quot quot virgin load AP associated with the void ratio from thie miression consolidation test In Figure 132 the virgin compression e curve or the field consolidation curve for clayey soils appears on a semi logarithmic diagram as a straight line This line can be represented by the following equation where CE is the dimensionless compression index Void Raiio Dru 39 9 an zf39 0Q a T Pg 391 4 A 4 39d i39 i im I 39539 W i k E3I EE3 gae e glen Pressure log scale 550 l E3 6 19 AP 3 2 ea quot Cc 10310 quotquotIquot Figure l32 From NAVFAC 1982 0 78 Engineering Geology a Laboratory Manual The virgin compression curve is established by extending the straightline part of the recompression curve By selecting two points eo po from the graph and using the value for e from the preceding equation CC can be determined by the following equation Ell 32 ti C e e P8 RM E pa Ap We iWi 10310 i Po where AH total settlement from consolidation Cc compression index Ht height thickness of compressible soil layer P0 original load A p change in load e original void ratio The time over which consolidation will occur uses some of the same information necessary for calculating the amount of settlement The be determined based on the permeability of the soil and the compression index using the following formula 1 b Y or my 2 in quot quot permeability of the compressible soil layer coef cient of consolidation compression index unit weight of water Once the coefficient of consolidation is determined the time for any portion of the expected total settlement can be calculated using the formula MMWWyWy it p9n p9n if n 3939 39 39u Mv39 2 h h cs B ii is B 0z 539 5939 if v t time required for the proportion of tota settlement to occur T time factor Z fi d maximum length of drainage path ea C coefficient of consolidation d 391W quot39l 2 Ht i quotll zwquot1quot tleg EXERCISE 13 Soil Compressibility 79 Typically the time of interest is when 90 percent of the total settlement will have occurred Therefore the vlhe of T is usually 090 The value for T is derived from graphs relating percent of total settlement to changes over time in pore water pressure The maximum length of the drainage path d will depend on the thickness of the compressible soil layer H and whether drainage is one way or two way one Way drainage would be expected when the compressible layer has a permeable layer above and an impermeable layer below The water from the compressible layer would drain vertically upward For one way drainage the maximum length of the drainage path is equal to the thickness of the soil layer H If a permeable layer was present both above and below the compressible soil layer then two way drainage could occur For t the maximum length of the drainage path is equal to one half the thickness of the soil layer H 393939Tquotquot39 3939quot39quotquotquotquot3939quot These formulas represent basic computation of settlement due to consolidation and time for settlement to occur Consolidation theory provides for recon guring these formulas to address nonvertical drainage and other conditions which may be encountered in practice More thorough discussion of calculating settlement can be found in Bowles 1979 and NAVFAC 1982 is the term applied to arti cially compressing soil to change its volume This is 0 by applying momentary loads The momentary loads are created by mechanical devices which roll tamp or vibrate over the soil Compaction reduces the voids to achieve some improvement in the engineering behavior of a soil Compaction might be used to inggase the soil bearing strength for a or to dmr gLl1epamwbm d to form an earthen dam I des compaction will depend on the needs of the engineert project and the character of the soil being used The particlesize distribution of the soil being used for a project places limits on the degree of compaction which can be expected Compaction can be facilitated by the water content of the soil m ter increases resistance to the reorientation of soil particles necessary to reduce the volum of b This results from the surface tension of water between the individual soil particles T much water will result in x that initially 1 ist the momentary loads and leae C 9 1 of voids in the soil P t 9 e right amount of water in the soil to reduce frictional resistance and permit compaction is termed the Epfimum moisture content The optimum water content and mltu 9aaerras1 LMusw 2aerrzs airs maximum dry density 39y for a MHT T13 speci c soil are determined by laboratory testing The laboratory results serve as the standard for P W later eld measurements during 39 the construction phase of the project Laboratory testing usually employs the Ijroctor or modi ed Proctor compaction tests quotln this F iiingj the soil sample is subjected to a prescribed number of blows from a hammer of a standard weight The water content associated with achieving the enSity Of e Figure 133 339gg scam snow A390 AI 9II SAND GRJWELY IInusquotnnu IE AIR VUIDS CURVE HSSIHEII is 165 EIHII39IquotV II NIOIBTUHI 80 Engineering Geology 1 Laboratory Manual soil it 3ptimumn1oismremntent Figure 133 on the previous page shows a representative graph from laboratory testing where moisture is plotted against density in pcf The optimum moisture content maximum dry density and specific gravity for the soil are determined from the graph The degree of compaction necessary will vary with the type of project For example compaction of a soil embankment may call jqr compaction levels which are 95 percent of maximum dry density for the S01 emg used Such a value may be a contract speci cation Percent compaction would simply be compaction The maximum M ll be known from laboratory testing of the soil Calculating the dry density of the soil yd would require determining the water content and moi t7fdry density of the soil E One method for determining these values is through theigcmd cone methodEA hole is dug in the compacted soil The hole is lled with a sand having a known density The weight of sand necessary to replace the volume of soil collected is measured The volume of the hole can be calculated by dividing the weight of the sand by its known density Because this involves dividing a weight value by one which is weight per unit volume the result is a volume measure The moist unit weight ym of the soil removed from the hole is calculated by dividing the weight of the soil removed by the volume of the hole The water content of the sampled soil is determined in the laboratory A part of the collected soil would be weighed After drying in an oven it would be reweighed Dividing the difference between initial and dry weights by the dry weight and multiplying by 100 the percent moisture content W of the sample is computed To calculate the dry density of the soil yd from this information requires using the following f i g L 0 2 sh gca 39 f u 3 mm Ii gig Q any B 5 Ym d K 33 II S d H S V 39 39r5 ab iquot kg at lwfirrs Q The percent compaction achieved simply requires dividing the dry density of the soil 7 determined from the sandcone procedure by the maximum dry density 39y determined by earlier laboratory testing for this soil Other means for measuring eld compaction employ devices such as the neutron probe and balloon density device Descriptions of these devices and the sand cone methbdcan be found in Carter 1983 PROBLEMS POROSITY AND VOID RATIO Using the formulas given in the exercise calculate porosity and void ratio based on the soil information provided You may wish to sketch a phase diagram to show the volume values ii EXERCISE 13 Soil Compressibility lilif ii 1 WW 2 81 1 G 1 m we adv Problem I P G A soil sample has been oven dried in the laboratory It completely occupies a 500 cm3 container It is known from calculations using weight relationships that the volume of voids is 169 cm3 Calculate the porosity of this soil sample and use the porosity to determine the void ratio N A quot A A A 43 4 7 lt39ei5 quotquot quotquotquot quot39WrL39zltquot55 s2quotquotiree i V ii Problem 2 Another ovendried sample has a unit weight of 175 gcc and a speci c gravity of 263 As noted earlier in the exercise the unit weight of water in metric units is 1 gcc Using the formula employing weight relationships determine the void ratio of this soil Based on the answer and the void ratio for the soil in Problem 1 is it likely the samples may be from the same soil I f y 1 2 2 CONSOLIDATION AND COMPACTION o y t 5 B 2 f f M I J Problem 3 3 3 gr E A small pond is being created by placing a com acted earth embankment across a narrow valley bottom This will produce a staticwlgadlof750 wkgimg An 18meter thick compressible soil layer is located between two permeable soil layers under the embankment Consolidation testing of the soil in this layer was done on samples taken from soil borings The test generated the following values M eo 078 39 39A 7 i s i W iamp C 023 fsfi M P0 9842 kgmg Pk M 0 Determine the amount of settlement that will occur from placing the embankment 39ascn 39 tn ii 39 3931 F 7 2 1 39 b If twoway drainage is assumed calculate the time fgr 9Q1 09 consolidation to occur ffll7 is 084 The coefficient of permeability kMohl the soil in the compressible layer is l mday well W2 r or 1 if i 3 R C quot 3 Cc Y39 0 Q2310 Ei 39bo c If the embankment was increased in height resulting in a load 3 times greater than the one 0 393 indicated in the first part of this problem what would be the amount of settlement p What would be the time necessary to achieve 90 09 consolidation under this larger embankment 5 7Q Problem 4 The soil being used to construct the embankment described in Problem 3 has a maximum dry density of 1700 kgm an optimum moisture content of 6 and specific gravity of 27 Compaction testing by the sand cone method removed 24 kg of soil from a hole and replaced it with 23 kg of loose dry sand having a known density of 1520 kgm3 In the laboratory the 24 kg of soil was oven dried The sample weighed 21 kg after this drying 82 Engineering Geology a Laboratory Manual a Determine the percentage of compaction for the ll at the test location b As contract inspector you must certify from the test that the contract speci cation of compaction to 95 of maximum dry density is being achieved Can you certify that speci cation is being met based on this test result QUESTIONS 1 What term is applied to settlement under a static load in ne grained soils which may occur over a signi cant period of time 2 What is the meaning of the term optimum moisture 3 Name two methods for determining eld compaction values APPLI CA T I ON S Prediction of soil settlement under a foundation is not always easy Often the dif culty arises more from variations in compressibility within the construction area than the amount of settlement which occurs Using different foundation construction techniques such as spread footings installation of piles or removal of soil may be necessary to ensure acceptable foundation conditions In contrast construction with soil using compaction measures is more controllable An engineering geologist must recognize the importance of compressibility as an engineering property of soil The actual computation of compressibility characteristics may be undertaken by a geotechnical engineer It is important for the engineering geologist to understand the variables used in computing compressibility to ensure site investigation adequately samples the soil used in consolidation or compaction testing The discussion of consolidation should make clear the need for the engineering geologist to carefully investigate the thickness depth and character of soil layers present where static loads will be applied Cited and Suggested References Bell F G 1992 Engineering prgperties of soils and rocks Butterworth Heinemann 345 pgs Bowles J E 1979 E11ysical and geotechnical properties of soils McGraw Hill Book Co 478 pgs Carter M 1983 Geotechnical engineering handbook Chapman and Hall 226 pgs Holtz R D and W D Kovacs 1981 An introduction tojgeotechnical engineeriig Prentice Hall Inc 733 pgs Hough B K 1969 Basic soils engineering 2nd Ed Ronald Press 634 pgs NAVFAC 1982 Design manual soil mechanics US Dept of Defense NAVFAC DM 71 Department Of the Navy 360 pgs 106 ENGINEERING SOIL MODULE 32 A compressible soil layer 12ttH thick is subjected to 1 static load 0 2000 lb Ag Ap 2000 16112 Pervious incompressible layer Pervious compressible layer Pervious incompressible layer Consolidation testing of the material yields Assuming twoway drainage compute the the following values time for 90 09 consolidation to occur 60 078 2 3 CC 023 z Tquot d Q88 6 1584 days P0 2016 lbft Cv 003 C 002 ftday Where d H 1 2 T 088 90 consolidation Determine the amount of consolidation that will occur AH HCC P0 9 A 1 ea P0 121023 LO 2016 2000 178 2016 12 023 178 Log 030 047 ft or 558 in 2 content in the soil can reduce this frictional resistance and facilitate com paction At the same time the soil should be as dry as possible Testing using the Proctor or modi ed Proctor compaction tests can determine 1 39 densities obtained for di erent water contents Optimum water content will be identified by this testing This is the water content ott e 501 w it is compacted to the maximum dry density Compaction testing involves placing a prepared soil sample in an appa ratus and subjecting it to repeated blows The hammer weight used and the height from which it is dropped from differ for various versions of the h Proctor compaction test For exact descriptions of this testing consult 3 AASIITO a I Density is determined from the sample by using 39 a penetration resistance test The moisture content is computed for this o39 aampnun EXERCISE 14 SEEPAGEANDDRNNAGE W ater strongly in uences the behavior of rock and soil for many engineering and environmental purposes Of particular interest is water within the saturated or phreatic zone of soil The phreatic zone represents the portion of a soil mass in which the voids are filled with water The water can be termed groundwater or phreatic water The water table is the plane marking the boundary between the saturated or phreatic zone and the overlying unsaturated or vadose zone Because the water table may uctuate vertically in response to wetting and drying events the phreatic zone dimensions will also change Figure l4l shows a well installed into the phreatic zone The height of water within the well above some datum plane represents the Vadosa zone total head h It can also be expressed by its Depth to water l V Water tabla 4 C1 two components elevation head z and E T T pressure head hp Elevation head is the E g 39 393939 32ff elevation of the bottom of the well above u g E some established elevation baseline Pressure E E J 1 head hp is the elevation difference between 1 the bottom of the well and the top of the 1 ii 2 water within the well It is represented by the 5 2quotquotE quotl WEquot elevation above one level 1 formula Figure 141 h z hp The principles of uid mechanics would show total head to be composed of the elevation head pressure head and velocity head The formula is simplified by eliminating velocity head This simplification is permitted because of the slow rate of movement by groundwater through permeable media Assuming the bottom of a well was 543 meters above the datum plane and the static level of the water within the well was 24 meters above the bottom of the well our total head would be h 543 24 567 m Figures l42 and 143 on the next page show two hillslopes each with two wells Water within the two wells in Figure l42 rises to the same level above the datum plane While the pressure 83 84 Engineering Geology a Laboratory Manual head differs between the two wells the total of pressure head and elevation head would show the same total head is present The water is not owing because groundwater moves in the direction of decreasing total head I q Distance hI I I I Total head 91 E E39 if F1 tTotaI head I Total head Iquotl Pressure head 7 Figure 143 I Ilt Total head L favd I I T E E L r 399 Am P39 Water in the wells in Figure 143 rises to different levels above the datum plane The total Figure 142 would decrease between the two wells 1nd1cat1ng groundwater movement 111 the general direction of the well with the lower total head This change in head over the distance between the two wells is the hydraulic gradient i Hydraulic gradient is calculated by the head loss h or difference in total head between wells divided by the horizontal distance L between them Assuming the head loss between two wells is 15 meters and the distance between them is 1000 meters the hydraulic gradient is 15 meters per 1000 meters This hydraulic gradient could also be represented as 002 meter per meter by dividing the denominator into the numerator This can facilitate comparison of gradients between wells set at different distances It is worth noting that when consistent units of measure are used for both numerator and denominator any other consistent units may be substituted without altering the value of the gradient Heath 1989 For example 15 feet per 1000 feet is the same hydraulic gradient as 15 meters per 1000 meters Hydraulic gradient may 39 also be converted to expressions with inconsistent units such as meters per kilometer or feet per W9quot 3 h 28 ml mile 6 It is possible with a third well to determine the 399 70 direction of groundwater movement as well as N W the hydraulic gradient Heath 1989 Figure 144 L is a planimetric view of three wells showing their wequot 1 320 m relative geographic positions the distances art 25 ml we 3 between the wells and the total head at each H 235 well Figure 144 EXERCISE 14 Seepage and Drainage 85 The direction of groundwater ow takes several steps to determine The first step is to identify the well with the intermediate total head value Second calculate the position between the well having the highest head and the well having the lowest head at which the head would equal that of the intermediate well This is accomplished by setting up the relationship where the total head at the intermediate well subtracted from the total head of the highest well over the unknown distance x equals the total head at the lowest well subtracted from the total head of the highest well over the known distance between them Solving this relationship provides the distance to the point from the well with the highest head toward the well with the lowest total head which equals the total head at the intermediate well The third step is to draw a straight line between the intermediate well and the point identi ed in the second step This represents the contour where total head is equal to the intermediate well Fourth draw a line perpendicular from that line to the well having the lowest total head This line parallels the direction of groundwater ow Remember the flow will be toward the lowest total head Use the direction information from the planimetric representation to establish the actual direction Once the direction of groundwater ow is established its hydraulic gradient can be calculated Subtract the lowest total head well value from the intermediate total head well value which represents the total head along the entire line drawn in the third step and divide by the distance along the line paralleling the direction of ow between the well and the intermediate value contour line This yields the hydraulic gradient Having established the direction of ow and its gradient the other variable which might be of interest is the quantity of ow Quantity of ow will be the volume of groundwater per unit time that is passing through a specific cross sectional area within the soil Computing the quantity of groundwater owing through a particular area uses a rearrangement of Darcy 5 Law a fundamental relationship governing groundwater movement The formula is QKAi where Q discharge in volume per unit time per unit area K hydraulic conductivity of the material i hydraulic gradient Hydraulic conductivity is defined in Exercise 12 A gure is provided in that exercise giving hydraulic conductivity ranges of several selected soils If the coef cient of permeability k were known for a material it can be substituted for the hydraulic conductivity factor in the formula P0re water pressure is a factor in many relationships defining the behavior of soils The pressure head component of total head can be used to define the pore water pressure present at the bottom of a well The pore water pressure pt is simply the pressure head hp times the unit weight of water 39yw as represented in the following formula uhY 36 Engineering Geology a Laboratory Manual It is important to remember the direction of decreasing pressure head may or may not correspond to the direction of decreasing total head For thisreason groundwater flow can be in the opposite direction of both increasing pressure head and pore water pressure Using the pressure head of 24 meters from the total head example given earlier the pore water pressure in the well would be 1 24 x 98 235 kPa kiloPascals Seepage pressure is a measure of the force moving groundwater places on a unit volume of soil Seepage pressure at a free face can be sufficient to dislodge soil particles This leads to erosion through piping In contrast to pore water pressure which relates the pressure head to the unit weight of water seepage pressure P5 is a function of the hydraulic gradient i and the unit weight of water yw as follows P i Y S Assume that the wells used in the earlier example problem to calculate hydraulic gradient were immediately above the cutslope of a road It might interesting to know the seepage pressure being exerted over a square meter of cutslope oriented perpendicular to the groundwater ow direction Substituting the hydraulic gradient of 002 meter per meter in our formula for seepage pressure P5 002 x 93 02 kPa This could be compared to data on the resistance of the soil present on the cutslope to seepage pressure to determine whether it might cause an erosion problem PROBLEMS Problem I The first monitoring well for a foundation study is completed The bottom of the well is 23 m above the datum elevation selected for the project The static water level in the well is stabilized at 8 m above the bottom of the well Determine the total head for the well Problem 2 A second monitoring well is installed 243 m away The elevation of the bottom of the well above the datum elevation is 29 m and the pressure head is 2 meters Which direction if any is the groundwater flowing between this well and your first well Problem 1 Problem 3 Two monitoring wells were established to determine groundwater conditions at a site under consideration as a future solid waste disposal site There is a distance of 330 m separating the g EXERCISE 14 Seepage and Drainage 37 wells which have total head values of 28 m and 13 m Calculate the hydraulic gradient for the site You are making a presentation to local government advisory board members who are more comfortable with English units of measure Convert the hydraulic gradient to English units Problem 4 One question raised for the future solid waste disposal site is the adequacy of the liner design The project engineer needs to know the seepage pressure Using the hydraulic gradient calculated in Problem 3 calculate seepage pressure in SI units Problem 5 Investigators of a leaked hazardous waste sute are concerned about possible migration we 2 of contaminated groundwater away from the h t 23 ml site Figure 145 is a map view showing f three wells installed around the site The total 8 U head for each well is given as in Figure 144 33 0 Determine the direction and hydraulic N gradient for groundwater ow CL Well 1 32 quot Problem 6 h t 26 ml we 3 h t 235 ml Settlement analysis for the foundation Figure 145 materials where the two wells in Problems 1 and 2 are installed requires pore water pressure information Using the pressure head values given for the wells in Problems 1 and 2 calculate the pore water pressure Problem 7 An excavation was made into a hillslope to level an area for a homesite The face of the excavation is 30 m long Groundwater seeps across the entire excavated face from to base to 5 m above the base Monitoring wells determined the hydraulic gradient to be 017 m m Testing established the material has a hydraulic conductivity of 11 galdaym2 Calculate the discharge per day from a m2 of the excavation face What is the quantity of water per day which must be intercepted to keep the site drained APPLICATIONS There are many reasons to calculate the groundwater variables discussed in this exercise As shown total head is necessary to establish that groundwater flow is occurring its direction and its gradient This information is relevant to designing drainage control for construction projects It is often required in investigation of hazardous waste sites If a contaminant reached groundwater knowing the water is moving and in what direction will guide study of the contaminant s migration Fi3939 vsI I39a39 39aE1W K r 88 Engineering Geology 21 Laboratory Manual Porewater pressure is a component of some calculations for soil compressibility and shear strength Porewater pressures increase when a normal load is placed on a soil Measurement of porewater pressure prior to loading and after would show the degree to which drainage was complete This information would verify the calculated time for settlement where a compressible soil layer was present Porewater pressure is a factor in de ning effective stress a concept discussed in more detail in Exercise l6 Effective stress is an element in defining the shear strength of a soil As noted earlier seepage pressure can cause erosion by piping Piping occurs where seepage pressure dislodges soil particles at a free face within the soil caused by an animal burrow decayed root or at an exposed surface at ground level The loss of particles enlarges the initial pipe leading to development of a large space or void in the soil This void may be unable to support the weight of overlying material which leads to collapse When this occurs under a structure like a road or within a structure such as an earthen dam the structural integrity is compromised Construction of structures or other uses may be impaired by too much water Where groundwater is the source of this water intercepting drains or other drainage techniques may need to be applied Effective design of drainage includes knowing the seepage quantity expected in order to be able to intercept enough water to produce the desired drainage LOOKING AHEAD Many of the calculation made from monitoring wells data can be determined through graphical representation This representation is called ow net analysis Flow net analysis is the subject of Exercise 15 In addition to permitting computation of groundwater information it provides a better representation of groundwater conditions between monitoring well locations Cited and Useful References Cedergren H R 1989 Seepage drainage and ow nets 4th ed John Wiley amp Sons 465 pgs Heath R C 1989 Basic ground water hydrology US Geological Survey Water Supply Paper 2220 84 pgs Johnson R B and J V DeGraff 1988 Principles of engineering geology John Wiley amp Sons 497 pgs Kenney C 1984 Properties and behaviours of soils relevant to slope instability Q Brundsen D and D B Prior eds Slope Instability John Wiley amp Sons pp 2765 WPRS 1981 Ground water manual U S Dept of Interior Water and Power Resources Service 480 pgs EXERCISE 16 SOIL SLOPE STABILITY t is important to know the strength of soil being used in construction Soil has a low strength compared to steel wood and many other construction materials Although this makes soil a less desirable construction material its abundance availability and ease of handling more than compensate for its undesirable characteristics Soil is often used as a foundation material This can take the form of ernbankments upon which roads railroad tracks or other structures are places Other examples of embankments constructed from soil are levees and dams Where these embankments are constructed with slopes or on slopes the stability of those slopes becomes a concern Estimating slope stability requires determining the shear strength present at the likely plane of failure within a soil One of the first steps in assessing slope stability is deciding whether the expected failure will occur on a circular or planar surface The characteristics of both the soil and site will establish whether a rotational failure on a circular surface or a translational failure on a planar surface occurs Analysis methods appropriate to either rotational or translational failures can then be applied There are too many methods available for detailed analysis of slope stability to address in this exercise The underlying factors affecting the shear strength of soil and the shgzg are the focus of this exercise These factors are the basis for any of the specific slope stability methods which may be used Shear strength is the strength characteristic which is critical to slope stability The fundamental relationship of shear strength is represented by the Mohr Coulomb failure envelope This concept is explained in Exercise 3 The Mohr Coulomb failure criterion is a linear equation 5 vmM tu ltw Em 9 It defines th tressAat the faiLUlegLagMithin the soil 7 Tf is usually replaced by s to represent shear strength The angle cl is the angle between the failure envelope and the horizontal This angle of internal friction or friction angle is a measure of the frictional resistance of the soil to shear failure as it was along the rock surfaces discussed in Exercise 9 It is defined by the angle formed between points of increased shear stress needed to produce failure at greater confining pressures Where the Mohr Coulomb failure envelope intercepts the shear stress axis of a Mohr Circle diagram it graphically defines the cohesion c of the soil Cohesion is the 39 strength attributable to the interparticle attraction within the soil It is independent of the normal stress applied to the soil As noted in Exercise 3 these values can be derived from subjecting soil samples to triaxial testing 94 W EXERCISE 16 Soil Slope Stability 95 There are a number of factors which can affect the shear strength of a soil These factors include 1 proportion of ne grained particles 2 the density or packing of particles and 3 water content Johnson and DeGraff 1988 A Cohesion or interparticle attraction is derived from the finegrained fraction of a soil As i described in Exercise 11 fine grained soils are termed cohesive soils The lack of cohesion in coarse grained soils simplifies the shear strength formula to g g 5 W S 0 tan b 5fShear strength for a coarse grained soil can be determined from its internal angle of friction and the expected normal stress eess imam 34 5 5 ta1 3 Density or packing of particles affects the void ratio Exercise 13 in the soil A lo9sely packed soil will have a l strength than the same soil when densely packed The denser packing reduces the void ratio and permits more interlocking of particles Interlocking particles p effectively increase the internal angle of friction Other physical aspects of the soil particles such 39 as shape surface roughness and grainsize distribution also will in uence the interlocking of particles quot quotquot quot39quot quot39quot quot quot fwm mm m The effect of density can be demonstrated with a coarse grained soil such as a well graded gravel GW A GW soil with a 25 relative density would have an internal angle of friction of about 32 The same soil with 75 relative density would have an intemal angle of friction of 40 Water content in uences the shear strength of cohesive and noncohesive soils When the water content nears a saturated condition or loading greatlyiuces the volue of voids hydrostatic V A or pore water pressure results This is due to thncpple naturepf W2t6139 COI1 Il6d11 1 the soil The normal SlZ1 3 1 L1c139 rQl13 f applied load is Evan amount equal to the pore water pressure p Exercise 14 This represents the eff 1 Kenny 1984 It W111 persist until the water can drain and pore water pressure is reduced to preload level The Mohr Coulomb failure criterion for this situation is represented as so ptan c II o E ective sz3essgt Exercise 3 is the actual stress in uencingfthejpghavior of the soil mass Resistance to shear stress is a function of the noriifal str ssapplied to theiHsi5li39Tm39a sZquoti l stress Where pore water pressure is present it reduces total stress for the reasons noted above The remaining resistance to shear strength is the effective stress To illustrate effective stress assume a soil mass which is 75 m thick The thickness of the soil was determined by drilling a well which did not encounter any water If the soil has a unit weight of 201 kNm3 the normal stress an is 96 Engineering Geology a Laboratory Manual This is the normal stress at the point 75 m below the soil surface This value would be substituted into the shear strength formula with the values for cohesion and internal angle of friction quot Later the well is checked and found to have water standing at alheight of 34 m above the well bottom This pressure head permits calculation of the pore water pressure u by multiplying the pressure head by the unit weight of water Exercise 14 A p 34 m 98 kNm3 333 kPa mww eitw M lt 5 29 1 A ftgmffective stress qai at the point 75 m below the soil surface is now the total stress reduced by the amount of porewater pressure This means the normal stress available to substitute into the shear strength formula is no longer 1508 kPa but 1175 kPa This clearly represents a signi cant decrease in the shear strength of the soil mass This would be especially important in a coarse grained soil where shear strength is dependent on the internal angle of friction With this understanding of shear strength the problem of analyzing slope stability can be addressed Slope stability analysis is an attempt to establish the threshold at which the slope will fail on either a circular or planar surface This threshold represents the point where the force of gravity acting on the soil mass overcomes the resisting force of the soil mass This threshold can be represented as the factor ofsafety F5 for the slope By de nition a factor of safety of 10 is the value at the time of failure In other words when the balance between shea1strltss applied to the slope equals the shear resistance slope failure occurs Because of this fundamental relationship most slope stability methods use shear strength and values to calculate the factor of safety 3 3 gt 9 r 1 A quot39 quot l5D 5 l quot Factor of safety is not a value with a de ned scale A factor of safety of 40 does not actually mean you are two times less likely to have a slope failure than a factor of safety of 20 It is suggested that the minimum factor of safety which you need for a slope is based on the uncertainty of the soil strength measurements and the cost and consequences of a slope failure Duncan and Buchignani 1975 A factor of safety of 20 or greater may be desired where the uncertainty of strength measurements is great due to complex soil conditions inconsistent or incomplete strength data the cost of repair is much greater than the cost of construction or the slope failure would endanger human life or valuable property In contrast a factor of safety of l2 i may be acceptable where little uncertainty of strength measurements exist as with uniform gaitquot conditions and highly reliable strength data and when the cost of repair is comparable with the cost of construction and no human life or property is at risk from a slope failure Analysis of slope stability will be illustrated by slope stability charts These are simple procedures which can be used in the eld for preliminary assessment Chart solutions utilize the same factors as more detailed analysis techniques The need to assume simpli ed site conditions and soil characteristics limits their reliability More detailed analysis methods can incorporate the complex site conditions and soil characteristics which often are associated with a slope stability question Figure 161 on the following page de nes the elements for a chart stability solution for a rotational failure in cohesive soil It is assumed that shear strength is derived from cohesion and I is constant with depth The soil mass is homogeneous throughout its total depth It is also EXERCISE 16 Soil Slope Stability assumed that 1 there is no open water submerging part of the slope 2 no surcharge placed on the top of the slope or 3 no tension cracks on the top of the slope Failure may be on an are which passes through the base we or slope Fig 162 As an example a slope having a angle of 35 has a height H of 76 m from the base of the slope to the top The soil extends to a depth D of 61 m below the base of the slope The total unit weight 39y0f the cohesive soil is 184 kNm3 which is equal to 1840 kgm3 The cohesion c of the soil is 2929 kgmg The first step is to calculate the value d which is used in the stability chart to nd the stability number and establish the expected mode for the failure circle This is done by using 97 ama thc DdH Totol unit wt 7 T Firm mtl 4 C Factor of sofety FSN o 7TH Figure 161 SLOPE TOE Cl BASE CIRCLE CRCE ROLE D 61 08 H P Z Flgllf In Figure 163 find the curve 11 C H representing 08 Locate the Fquotquot 39 quot 39 quot F quot05 1 1 f Y 39 intersection of this curve with the 10 3939F39j3 L I1 39 i ase CI39C es SLOPE 39 39 1 39 slope value of 35 degrees Extend Q Slopecifcles CIRCHE am 1 39 g a point horizontally from this d 3 Wm J 39 AM I 5 intersection to the vertical axis of E H 2355 J F 39 39 E 39 8 w ig P I I the chart to determine the stability 20 Firm base l 1 ezgy Ll BASE I I f 7 a 9 I 390 I numbgr No In thls Case the E 7 ytotaunitweightolsol 0 l 3 mltrOJbJrL CIRCLE u o 1 39 T 4 39 139 1 39 o Stablllt number 1S 58 Note the E 39 8 l J Z 39i TTLA I nK V 39439 field in which the intersection is 2 5 z A39 5 uc u3939 393953 Tr t 553 d located to determine the failure 5 5 Au G F L G circle mode It is a base failure 5 Gees Substitute the stability number and 4 A J other variable into the formula for 3183 L cot F factor of safety HC 0525 39o5o 075 To 15 2 33 6 10 0 ii L114 141 ii i H 114 90 80 70 60 50 40 30 20 l0 0 Slope Angle 5 deg l hpwp E 1 c 58 2929 Y H FS N I E F EEQ5 R J yw l84076 Figure 163 from NAVFAC 1982 after Taylor 1948 98 Engineering Geology a Laboratory Manual NAVFAC 1982 describes how this analysis could be applied to where two or more cohesive soils are present in the situation described in the above example It also provides additional charts which enable computing the factor of safety where surcharge or tension cracks are present in this slope s Similar stability charts are available for computing the factor of safety for translational failures on planar surfaces Slope stability for translational slopes is sometimes referred to as analysis of in nite slopes Duncan and Buchignani 1975 are a source of chart solutions for slope stability on in nite slopes NAVFAC 1982 also provides a simple wedge analysis procedure for computing the factor of safety for a potential translational failure PROBLEMS Problem I The total stress for a recently constructed 55 m thick earth embankment is 865 kPa at its base A well was installed to a depth of 55 m within the embankment for postconstruction monitoring After two storms the pressure head was measured in the well at 18 m and 27 m respectively What was the e1fecti yemspt139eb in the embankment afterthe two storms r git J 1 L J 3quot 39 K J b 2 0 p L L er 5 a quot539 If pre construction analys quotshowed failure could occur at the base of the embankment described in Problem 1 when total stress was reduced to 53 kPa or less what pressure head would be measured in the well to reduce total stress to that level Problem 3 You are evaluating a section of a pipeline project which will create a cutslope in cohesive soil which has a unit weight of 1642 kgm3 and cohesion of 2894 kgm2 The height from the base of the slope to the top of the cut will be8mr 1 Earlier borehole drilling indicates the same soil extends to a depth o12i m below the base of the cutslope Because excavation costs are less for steeper cutslope angles you must consider whether to have the cutslope at an angle of 15 25 or 35 Using the stability chart information provided in Figure 163 determine the factor of safety for each angle and the likely mode for rotational failure mw m Your borehole testing and surface mapping show the soil to be fairly uniform Laboratory testing of samples you collected have yielded consistent values This section of the pipeline passes through an unpopulated rural area used primarily for summer cattle grazing What is the slope angle you would choose which provides for an appropriate factor of safety and excavation cost State your reasoning Q UES TIONS 1 What is the term which describes the reduced strength resulting from water content nearing saturation in a soil ll 39 a H H EXERCISE 16 Soil Slope Stability 99 2 Name the two components of the Mohr Coulomb formula which represent the shear strength relationship in soil and identify which one is absent in coarsegrained soils 3 Name the two types of failure which may occur in soil 4 What is the term applied to describe the threshold point where the force of gravity acting on the soil mass overcomes the resisting force of the soil mass APPLI CA TI ON S Understanding effective stress provides a means for conceptualizing the effect of water on slope stability For example cohesive soils are nearly always partially saturated This is due to the low permeability of soils with high clay content If an embankment such a fill slope for a road is placed on a slope with a cohesive soil it increases the load This increases pore water pressure in the cohesive soil by reducing void space As a result effective stress is lower Lower effective stress means the chance of failure in the cohesive soil is greater shortly after the embankment is placed If failure does not occur the pore water will drain reducing the pressure head The resulting increase in effective strength means slope stability is improved in the long term The reverse is true for a cutslope in the same cohesive soil The short term effect of the cutslope is to drain or lower pore water pressure This increases effective stress and slope stability in the short term However long term adjustment of the groundwater can result in a higher pore water pressure This higher pore water pressure could reduce effective stress enough to cause failure in the cutslope Chart solutions permit rapid assessment of slope stability More importantly they illustrate the significant variables used in more detailed slope stability analysis Slope steepness soil unit weight soil thickness pore water pressure surcharge and tension cracks must be used in more detailed analysis methods A full understanding of their relative in uence on slope stability ensures the proper assessment method is applied to a specific situation It is easy with computerized slope stability programs to become mesmerized by the numbers and fail relate the analysis fully to the on the ground situation If possible try sample problems on computerized slope stability programs such as PCSTABL 4 Kopperman and Carpenter 1985 or programs on programmable calculators such as quotSSMOSquot Prellwitz 1985 Often these slope stability methods can be applied to existing landslides to establish conditions at the time of their failure This back calculation is very useful for determining pore water pressure and similar variables which are difficult to measure following failure A better understanding of the conditions leading to failure at a site leads to a better remedial design to stabilize the slope instability Cited and Suggested References Bell F G 1992 Engineering properties of soils and rocks 3rd ed ButterworthHeinemann 345 pgs Duncan J M and A L Buchignani 1975 An engineering manual for slope stabilitvitudies Dept of Civil Engineering University of California Berkeley CA 83 pgs 39 39x a 100 Engineering Geology a Laboratory Manual Hunt R E 1986 Geotechnical engineering techniques and practices McGraw Hill Book Co 729 pgs Johnson RB and JV DeGraff 1988 Principles of engineering geology John Wiley amp Sons 497 pgs Kenney C 1984 Properties and behaviours of soils relevant to slope stabi ir1 Slope Stability Brunsden D and D B Prior eds John Wiley amp Sons pp 2765 Kopperman S and J R Carpenter 1985 PCSTABL 4 user s manual Federal Highway Administration Report FHWA TS85229 Washington D C 100 pgs NAVFAC 1982 Design manual soil mechanics US Dept of Defense NAVFAC DM71 Dept of the Navy Washington D C 360 pgs Prellwitz RW 1985 SSMOS Slope stability analysis by three methods of slices with the HP4l programmable calculator USDA Forest Service Report EM 71707 Washington DC 66 pgs Taylor D W 1948 Fundamentals ofsiiailfiriiiechanicsz John Wiley amp Sons Inc 700 pgs W EXERCISE 16 Soil Slope Stability assumed that 1 there is no open water submerging part of the slope 2 no surcharge placed on the top of the slope or 3 no tension cracks on the top of the slope Failure may be on an are which passes through the base me or slope Fig 162 As an example a slope having a angle of 35 has a height H of 76 m from the base of the slope to the top The soil extends to a depth D of 61 m below the base of the slope The total unit weight 39yLOf the cohesive soil is 184 kNm3 which is equal to 1840 kgm3 The cohesion c of the soil is 2929 kgm2 The first step is to calculate the value d which is used in the stability chart to find the stability number and establish the expected mode for the failure circle This is done by using 97 Cval0 uquot 9 DdH Total unit wt 7T Firm mtl 5 Factor of sofety FSNO77quotH T Figure 161 SLOPE CIRCLE TOE CIRCLE BASE CIRCLE T T W 08 H Figure l62 In Figure 163 nd the curve ii C M 3 representing 08 Locate the Fa 39 395alquotquot F N EJ rquotLfiI r intersection of this curve with the 10 T quot quot5 i 7i739J U Base CIFCTBS 51oigtE J I 39L i L slope value of 35 degrees Extend 9 SOpemes ClFlCLE 71111 iii a point horizontally from this d 3 77777 T rquot 39lL 3939j intersection to the vertical axis of 8 T L1 6839I T r I 7 quot 39339 39 391 the chart to determine the stability 20 Firm base TM T nquotquot A P BAS 39 7 o 9 c C number NO In this case the 3 7 7v7i c il39t ir T gni l olf39 I gig u39r ClFiCL FT I 1 I 7quot s t number is 58 Note the E l 3 3 3912 J V 39 39 39 439 field in which the intersection is g 5 W Zquotquot located to determine the failure 3 I E 39 391quot quot quot s 351 circle mode It is a base failure 5 Og quotT i Y Substitute the stability number and Ar L other variable into the formula for 4 383 Cor J f3Ct0T Of safety 025 050 075 E0 15quot 2 3 1 5 100 0 1 LLL J 1 1 L 1 7 1 L1 1 L Li lLl 90 80 70 50 SO 40 30 20 O O Slope Angle 13 deg Figure 163 from NAVFAC 1982 after Taylor 1948 hr Vilquot c 2 2 FSN 58 S y H 184076 oil 3 2 39IgI 0 u p x firm has same practical suggese tiens an haw engineers ean re line their eentraets for minimum expeeurei Heuer an architect an atterney eautiens thatthe wards in his quotEeneraet Language Labquot are generic snggestiens T e net seeeifie language eheiees Thenqh engineers are aware ef Heneej hear la mindenen FE standard eentraet eeuments and Vlawlng gr C mstru tlng can Ehe rec memae HEE by their prE tracts to eensult year atterneya fessienal seeieties amany still use er aeeept nenetan er een tracts equentlyg Ehese engineers epen themselves up te increased liability expesufe Professionals shenl be aware that the wreng were er ghrase can bring their firms dawn around theme Else remember Ehat technical wards take their teehnieal meanings Cemmen wards take their eemmen meaning Contrast language sheuld reflect what yen and the eenere agrees en Genres will rea an intergret eaery were in a eentraet literally Charles R Hener ef Eaves net in the eenteat ef in ustry manta a Beatenbased eensulting usagei Language e be Avei ed ji Eub tituta La guage ALL F SEmI la EE ieIIrhg efgtsmagtep e eaLE l1 mee atiaeteaa imeewelsraten eased aeemf ia by the engieer in the exereieezef its prefee sies j4asut Hsallehemsbamee Iler nsnnLc n e ant ahitigw quot e Etn y wi h all rules The engineer shall esignEheprnjeet inaEere lame Ema vvtiens l EEWifh39 M 3fU1EE Lmeaandnaaiiins a ieh1 E2eng ne39shaLLTwe mem mil niie enaeeeefixefennnejitsgn isekxal seeaee asIE g39m iarJe te1ieeesn1effiaegeet ICEmM Ei l m E L Tnengnnea aedlpe erexstnxnien ke mge and e na in enm jan and eaa iiea xe as ngeia 3 gamd e by the eaaeaeenrreq res eng eees39 muselrqmali laleamaaetesaar teumneeeatnezanjes pa eneeaieene3939cne quotamp s e gef E ch yH R e eaaeny time at E efineej intervals wnneeenee appaepriaee ey he engineer in the eaereiseeef its pre ee 39s Ie1 jsavgfn eentinued en page 6 ENGINEER HG CliFFij GE S PgDMINIETRAT1 DN39 z 39QE Lang39uage ta AtvaaTdEri E3 MbEtit39l1tE Language I X T z 6y S 39 0 w p t G z y a of ue pmjezzt J l P z snf P x y 0qy pc 0qy y 7x 39 z P z v v m W y Ehe x P y x Bz y x p w x x s ta 0 y of w z t z z Ez x czar B B s Pft y levels A s V 39 Delete p v an z y y y v y v 0xr PHx x 4y z y 39 Le A y r e ntm nair as p x Bt N p q x w of its Vrafesaimal Uaua ly mare t u crzurse rriaquotI l cely S r 1255 less r v r q h mra r p Vs ate p ue r E3IEELTiI239 cf its fessictial j r e393 L Fl1EI39quotE39E pg Practimhla 11 prznssiblex 0 p 0c P R i 7 71 r In P T le 6 saf Cli lf z Wnaserve reuriew p T trait and tsza Y best emf b Iltn1w1e o 2 d PH state E ENGINEERING GEOLOGY USC Soil Classes and Land Use GW good subbase and concrete GP good subbase and concrete GM Wash GC Wash high terraces SW river sands SP Wind sands SM great to build on SC Wash 9 problem to build on ML loess good to build on erodible Missoula oods CL slope stability problems glacial marine MH really bad stability problems CH really bad expansive soils OH Weak OC weak Septic tank good G SW SP ML bad MH CH CL GC SC quot1f ow FC ecl Dvdex V MQWM 3 S 5 M39j 3C VH3 T w V Plcx94w39fc p p Pm z A CMJZ m 3 Cl 3 5 0 Lg F WOOIr T Feat 0 j PL 3 ENGINEERING GEOLOGY quotConstruction Materialsquot 1 Dimension Stone Production in USA 1989 a IXBE tonnage Value million 1 1 granite 37 46 2 limestonedolostone 31 18 3 marble 4 3913 4 sandstonequartzite 17 11 4 slate 8 9 5 others 3 3 2 Aggregate Production in USA 1989 1 Exp tonnage Value million S limestone 73 73 67 trap rock basaltdiabase 10 11 granite 9 9 marble 2 2 sandstonequartzite 3 4 others 48 7 7 a4 a u I vuivrqr r34Bf39u 362 BULLETIN OF THE ASSOCIATION OF ENGINEERING GEOLOGISTS 3 H 6 quot Q 1 I A if 0 g 1quot 1 QEJID 3 Gal Qt Ob Qu Om qrn di EXPLANATION QUATERNARY DEPOSITS Stream gravel and valley fill Talus and high angle alluvial cones Deposits of Lake Bonneville Q quot39 Undifferentiated alluviurn 5 quot Glacial moraine o lw CRETACEOUS OR TERTIARY um PLUTONIC ROCKS Quartz monzonite of Little Cotton wood stock Diorite in Bells Canyon U quot1 PALEOZOIC Pzl Gray crtnoidol limestone 39 43 at g r quotn39 sf 2quot PRECAMBRIAN p bc Big Cottonwood Formation quartzite interbedded with sholes and siltstones Quortzite unit Shale or siltstone unit Little Willow Formation quartz schist interbedded with biotite schist Lenses of chlorite amphibole schist SYMBOLS Contact dashed where approximate dotted where concealed quot39 Fault dashed where approximate dotted where concealed U up thrown side Thrust fault sowteeth on upper plate Strike and Dip of beds P6 overturned beds 6 Figure 1 Conventional geologic map part of Draper Quadrangle Utah From Crittenden 1965 KEATON GENESISLITHOLOGYi QUALIFIER 3 6 3 u 3 ll ll 3 iivIV d 0 r5 EXPLANATION UNCONSOLIDATED MATERIALS GENERAL SYMBOL Abcl EXAMPLES Agsn1fAlluvial material composed of gravel sond A genetic symbop and sill forming on alluvial fan in Lithologic symbol CrmbioCol luviol deposits composed of rock rubble C Quanfier symbol in a matrix of silt to boulders forming talus GENE C SYMBOLS Gmb1 Glacial till composed of silt to boulders A A F 39 39 G 39 G39 l 39 BEDROCK MATERIALS 3 Col luvlol L Locuslnne E ECHO DI Diorlle ELS Limestone UTHOLOGIC SYMBOLS GR Gronmc rock chiefly quartz monzonife b Boulders E m Sm QT Quortziie SC Schist g Gravel s Sand C ST 5 m ne39 QUALlFlER SYMBOLS SYMBOLS p quotquot FUN quot39 I Cgnfqcf lo Oufwosh U0 39 Talus lJ Fault dashed where approximate dotted D where concealed U on up thrown side Lun Thrust fault in bedrock so teeth on upper plate T35 Strike and Dip of beds fgooveriurned beds Figure 2 Engineering geologic map part of Draper Quadrangle Utah Modi ed from Richmond 1964 Morrison 1965 and Crit tenden 1965 G470570 ZOO SOIL SAMPLE LAB Your Name Score 1 In this lab we will be using Exercises 11 and 12 in the book and parts of 13 I will review a couple of important concepts You will work up the data for the soil samples we took earlier Do answer the following for the zoo samples worth 10 points Due next week 2 Your soil Team Your Soil Sample 3 Color a Numbers Moist b Name 4 Percent Moisture W lab72 5 Bulk Density a Dry v 230 cc b Moist 6 Unit Weighta Dry BD x 624 b Moist c Saturated 7 Atterberg Limitsa PL b LL c PI 8 Particle Size a Passing 4 b Passing 200 9 Classification a USC b AASIITO c USDA lO Void ratio e lab p 76 11 Degree of Saturation S lab p 72 l2 Estimate C and phi c phi
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