Geology Applied to Civil Engineering 土木工程地質(zhì) 英文課件 第11、12章 Geologic problems、Geological investigation

110GeologicproblemsinslopeengineeringGeologyAppliedtoCivilEngineering123contentsFactorsinfluencingSlopeStabilitySlopeStabilityAnalysisFailurepatternofArtificialSlope4CountermeasureforPreventingSlopefailure231FailurepatternofArtificialSlopeTheclassificationofthebasictypesofslopedeformationandfailureisthebasisforthestudyofslopestabilityandslopestabilization.FailurepatternsofsoilcuttingslopeAccordingtothescaleoffailures,thephenomenonoffailuresinsoilcuttingcanbedividedintotwomaincategoriesa)BenchfacefailureThemaintypesofbenchfacefailureincludesurfaceerosionandsurfaceslumping.Erosionisthephenomenonofrainwaterrunoffontheslopecarryingawaylooseparticlesfromtheslopeduetodynamicaction,oftenformingstripedgulliesontheslopesurface.Slumpingismostlycausedbyexcavationdisturbance,rainwaterleachingandscouring.Patternsofbenchsurfacefailureonsoilcuttingslope;(a):Surfaceerosion;(b):Surfaceslump41FailurepatternofArtificialSlopeFailurepatternsofsoilcuttingslopeb)SlopebodyfailureItreferstotheoverallfailureoftheslope.Overallslopecollapseandlandslidearebothslopefailure.Continuoustensioncracksandsinkingatthetoporupperpartofasoilslope,orbulginginthemiddleorlowerpartofaslope,aresignsofoverallslopefailure.Ingeneral,thistypeoffailureoccursduringoraftertherainyseason.Inthecaseofweaksubstrates,theslopefailureisoftencombinedwiththefailuretothesubstrate.Forthistypeoffailure,forecastingshouldbestrengthenedduringthewarningperiodtopreventaccidentsfromoccurringunawares.Thecauseofthefailuremustbeidentifiedbeforetreatment,andtheexcavationmustnotbeclearedatwilltoavoidfurthercollapseandexpansionofthefailure.51FailurepatternofArtificialSlope(2)FailurepatternsofrockslopeRelaxationRiverundercuttingormanualexcavationcausesagradualreductionintheminimumprincipalstressintherockandsoilbodywithintheslope,andtherockbodyatthesuperficialpartoftheslopesurfaceevenchangesfromathree-waystresstoatwo-waystressstate.Duringthisprocess,aseriesofsteeplydippingtensionfissuresareoftencreatedintherockbody,whicharenearlyparalleltotheslopesurface,andaregraduallypulledapartandopened.Relaxationofunloadingduetooccurrenceofexcavationinajointedrockslopeoutcroppedsandwichbetweenlimestoneandsandstone61FailurepatternofArtificialSlope(2)Failurepatternsofrockslopeb)CreepCreepisthelong-termslowdeformationofarockmassundertheactionofgravity.Thistypeofdeformationmostlyoccursinsoftandweakrock(suchasshale,micaceousrock,schist,etc.)orsoftandhardinterbeddedrockbodies(suchassandshaleinterbedded,shaletuffinterbedded,etc.),oftenformingflexuraldeformation.Superficialcreep;Deepcreep.Bendingcreepdeformation71FailurepatternofArtificialSlope(2)Failurepatternsofrockslopec)SpallingSpallingisaphenomenoninwhichtherockofaslopeisafailurebylong-termweatheringandthesurfacerockisbrokendownintorockchipsandsmallpiecesofrockthatrolldowntheslope.Themainreasonforspallingisthedestructionoftherockstructureduetovariousphysicalweathering.d)SlipfailureSlipfailureisaphenomenoninwhichtherockonaslopemovesdownwardsalongacertainfaceorbelt,anditisoneofthecommonformsofdeformationfailuretorockyslopes.Thespecificformsoffailureinslopesaremostlydownwardslidinganddouble-sidedwedgesliding.e)CollapseandRockfallCollapseisthesuddendownwardfallofamassiverockmassonasteepslopeundertheinfluenceofgravity;whilearockfallisthedownwardfallofanindividualrockmass.82FactorsinfluencingSlopeStability(1)RockandsoilpropertyThestabilityofrockslopesismoreclearlyrelatedtothetypeofrockthatmakesuptheslope.Ingeneral,magmaticrocksarestrongerthansedimentaryrocks;paramorphicrocksmetamorphosedfromsedimentaryrocksarestrongerthantheoriginalrocks(e.g.quartziteisstrongerthanquartzsandstone),andtheslopestheyformcanbehigherandsteeper;slopesofasinglelithologyaremorestablethanthoseofcomplexlithology;fine-grainedrocksaremorestablethancoarse-grainedones;massiveonesaremorestablethanflakes;slopescontainingmorequartzandfeldspararemorestablethanthosecontainingmoremicaschist.Ifanalyzedfromlithologyalone,rockswithhighdensity,highstrengthandhighresistancetoweatheringcanformhighandsteepslopeswithbetterstability.92FactorsinfluencingSlopeStability(2)GeologicalstructureInareaswhereregionalgeologicalstructuresaremorecomplex,foldsarestronger,largefissurezonesaremoredevelopedandnewtectonicmovementsrelatedtoearthquakesaremoreactive,slopestabilityispoor.Inthevicinityofthefaultandthecoreofthefold,therocklayerisbrokenandthejointsaredeveloped,hence,thestabilityoftheslopeisalsopoor.102FactorsinfluencingSlopeStability(3)GeotechnicalcontextureSoilswithahighcontentofflakeminerals(e.g.expansivesoilscontainingmontmorilloniteandillite)areusuallymorelikelytoaffectthestabilityofslopes.Theinfluenceofrockstructureonslopestabilityissometimesdecisive.Thelaminatedandschistosesurfacespresentinsedimentaryandparamorphicrocksoftenbecomeslidingsurfacesforrockslopefailurewhenthetendencyoftherockissimilartotheslopesurfaceandthedipangleislessthantheslopeangle.Thecuttingcombinationofvariousdiscontinuoussurfacespresentintherockoftenconstitutesanunstableblockoftheslopeandaffectsthestabilityoftheslope.112FactorsinfluencingSlopeStability(4)GroundandSurfacewaterTheimpactofwateronslopestabilitycanbedividedintothreeaspects:firstly,thesofteninganderosionoftherockandsoilbywater,whichreducesthemechanicalpropertiesoftherockandsoil;secondly,theformationofhydrostaticandseepagepressure,whichchangestheforcestateoftheslope;thirdly,thescouringanderosionoftheslopebywater,whichdirectlyfailurestheslope.122FactorsinfluencingSlopeStability(5)WeatheringWeatheringreducesthestrengthoftherockandsoilmass,decreasesthestabilityoftheslopeandpromotesthedeformationandfailureoftheslope.Alargenumberofinvestigationshaveshownthatthemoreserioustheweatheringofthesloperock,theworsethestabilityoftheslope,andthesmallertheslopeangleforslopestability.Inthesamearea,thedegreeofweatheringisdifferentfordifferentlithologies.132FactorsinfluencingSlopeStability(6)EarthquakeTheimpactofearthquakesonslopestabilityismanifestedintwoways:changingthestressstateofthesloperock,increasingtheseismicforceinthedirectionoutsidetheslopeonthebasisoftheoriginalstressstate;causingtherocktopullapartorcausingtheoriginalclosedfissurestoopen,formingunstableblocksontheslopeandenhancingtheactionofsurfacewaterandgroundwater.(7)HumanactivitiesInadequatehumanexcavationofslopes,failuretovegetationandanthropogenicalterationofsurfaceorsubsurfacehydrodynamicconditionsallcancauseslopefailure.143SlopeStabilityAnalysisTheevaluationmethodsofslopestabilitycanbesummarizedintothreetypes:(1)engineeringgeologicalanalysismethod;(2)theoreticalcalculationmethod(formulacalculation,diagramandnumericalanalysis);(3)testandobservationmethods.(1)EngineeringgeologicalanalysismethodThemostimportantelementoftheengineeringgeologicalanalysismethodistheanalogicalmethod,whichisthemostcommonandpracticalmethodofslopestabilityanalysisinproductionpractice.Inpracticalengineering,itisalsocommontoestablishanempiricalformulatodeterminethestabilityofslopesthroughalargenumberofstatisticalanalyses.Theempiricalformulaforthestabilityslopeofgeneralroadrockslopesestablishedisasfollows:153SlopeStabilityAnalysis(2)MechanicalcalculationmethodThemechanicalcalculationofslopestabilityisawidelyusedmethodforderivingquantitativeexpressionsofstabilityandisoftennecessaryforengineeringpurposes.AnalysismethodsforstabilityofsoilcuttingslopeForslidingfailureonsoilcuttingslopes,stabilitycalculationscanbecarriedoutbasedontheanalysisoftheaboveinfluencingfactors.Differentstabilitycalculationmethodscanbeusedfordifferentslipsurfaceshapes.CalculationofstabilityofsoilslopeswhentheslipsurfaceisflatSlopesmadeupofhomogeneoussandyorpebblysoils,etc.andslopesmadeupoflayersofnon-homogeneoussandysoils,haveanearlyflatslidingsurfacewhenfailure.163SlopeStabilityAnalysis(2)MechanicalcalculationmethodAnalysismethodsforstabilityofsoilcuttingslopeII.StabilitycalculationsforsoilslopeswithcircularslidingsurfacesAccordingtoalargenumberofobservations,theslidingsurfaceofacohesivesoilslopeissimilartoacylindricalsurfacewhenslidingfailureoccurs,andcanberegardedasacirculararcinthesection,calledasliparc.Themethodoftenusedtocalculatethestabilityofaslopewithacircularslidingsurfaceisthestripdivisionmethodinsoilmechanics.173SlopeStabilityAnalysis(2)MechanicalcalculationmethodAnalysismethodsforstabilityofsoilcuttingslopeIII.SwedishmethodTheearliestandsimplestmethodofbarsplittingistheSwedishArcMethod(SAM),alsoreferredtotheSwedishmethodorFelleniusmethod.Thebasicassumptionsare:Thesoilstabilityisaplanarstress-strainissue,whichonecertaincross-sectioncouldbeanalyzedastheexample.thefailurezoneofsoilisacylindricalsurfaceandslidingsurfaceofthecross-sectionoccurasanarc.Inaddition,slipmassisconsideredasrigidwithoutinteractionforcebetweenslices.SchematicillustrationoftheFelleniusmethod183SlopeStabilityAnalysis(2)MechanicalcalculationmethodAnalysismethodsforstabilityofsoilcuttingslopeIII.SwedishmethodTheempiricalformulaisasfollows:where:Wi－weightofsoilcolumnαi－bottominclinationofsoilcolumnli－bottomarclengthofsoilcolumnui－porewaterpressureontheslipsurfaceciand?－IndexoftheeffectiveshearstrengthSchematicillustrationoftheFelleniusmethod193SlopeStabilityAnalysis(2)MechanicalcalculationmethodAnalysismethodsforstabilityofsoilcuttingslopeIV.BishopmethodDifferenttotheFelleniusmethod,adevelopedmethodforevaluatingtheslopestabilitynamedBishopmethodconsidersthehorizontalinteractionforcebetweenthesoilcolumns.ThefactorofsafetyKcanbecalculatedasfollows:WhereQiisweightofsoilcolumnhorizontalresultantforcebetweensoilcolumns,othersymbolsarethesameasbefore.SchematicillustrationoftheBishopmethod203SlopeStabilityAnalysis(2)Mechanicalcalculationmethodb)AnalysismethodsforstabilityofsoilcuttingslopeI.StabilityofplanarfailurePlanarfailurealwaysoccursonthesinglestructuralplaneandgeometrywascharacterizedbythestructuralplanedipoutsidetheslopeandadip-anglelessthantheslopeangle.TheFactorofsafetyKcanbecalculatedasfollows:Schematicillustrationforplanarfailureofarockslope213SlopeStabilityAnalysis(2)Mechanicalcalculationmethodb)AnalysismethodsforstabilityofsoilcuttingslopeII.StabilityofwedgefailureWedgefailureisakindofcuttingblockarousedbytwogroupsofstructuralplanesaswellasslopesurface.TheFactorofsafetyKcanbecalculatedasfollows:where:?1and?2－frictionanglesontwoslipsurfaces,respectivelyc1andc2－cohesionontwoslipsurfaces,respectivelyα－dipangelofthelineintersectedbytwoslipsurfacesL－lengthofthelineintersectedbytwoslipsurfacesSchematicillustrationforwedgefailureofarockslope224CountermeasureforPreventingSlopefailureAtpresent,therearethreemaintypesofengineeringmeasurestoincreasethestabilityofslopes:improveslopeengineeringgeologicalconditions;passivereinforcementmeasures;andactivereinforcementmeasures.(1)ImprovingtheengineeringgeologicalconditionsofslopesThiskindofengineeringmeasuresmainlyimprovethestabilityofslopebychangingtheshapeofacoastalslope(suchasslowingslope,cuttingandreducingload,backpressureofpileload,etc.),hydrogeologicalconditions,geotechnicalphysicalparametersandvegetationconditions,forexample.Schematicillustrationofloadingandgrading234CountermeasureforPreventingSlopefailure(2)PassivereinforcementmeasuresThistypeofreinforcementcannotactivelyexertforcesontheslope,butreliesonitsowngravityoritsembeddednessinthegeotechnicalbodytoresisttheresidualslidingforcesorearthpressureofthegeotechnicalbody.Thistypeofreinforcementcanonlyplayareinforcingrolewhenthegeotechnicalbodyoftheslopeisdeformed,soitiscalledpassivereinforcement.Anti-slipretainingwallsAccordingtothenatureandtypeofslidingandtheforcecharacteristics,materialandstructureoftheanti-slipretainingwall,theanti-slipretainingwallisdividedintogravity-typeanti-slipretainingwall,anchor-typeanti-slipretainingwall,reinforcedsoilanti-slipretainingwall,sheetpileanti-slipretainingwallandothertypes.Anti-slideretainingwall;(a):Schematicillustration;(b):Practicalengineeringapplication244CountermeasureforPreventingSlopefailure(2)Passivereinforcementmeasures(b)Anti-slippilesTheanti-slippileisanengineeringstructurethatkeepstheslopestablebytransferringtheslopethrustbornebytheupperpartofthepiletothelateralgeotechnicalbodybelowthepile,relyingonthelateralresistanceofthelowerpartofthepiletobeartheslidingforceoftheslope.Anti-slidepile;(a):Schematicillustration;(b):Practicalengineeringapplication254CountermeasureforPreventingSlopefailure(2)Passivereinforcementmeasures(c)ActivereinforcementmeasuresActivereinforcementmeasuresapplypre-stresstotheslopegeotechnicalbody,restoringitsthree-wayforcestateandthusenhancingslopestability.Theeffectofthistypeofmeasuredoesnotrequirethedeformationoftheslopeasaprerequisite,butratheractivelylimitsthedeformationoftheslope.Atpresent,themainreinforcementmeasuresofthistypearepre-stressedanchorcables.Pre-stressedanchorcables;(a):Schematicillustration;(b):Practicalengineeringapplication課后學(xué)習(xí)及作業(yè)1.將“地震荷載對(duì)巖體邊坡穩(wěn)定性的影響主要是由于地震慣性力導(dǎo)致邊坡整體下滑力加大，降低了邊坡的安全系數(shù)口。”譯為英語(yǔ)。2.Howtoanalyzethestabilityofslope?3.Whatcanyougetfromtheprologueinthischapterofthetextbook？2612GeologicalInvestigationforCivilEngineeringGeologyAppliedtoCivilEngineering12contentsOfficeReconnaissanceSubsurfaceExplorationObjectiveandProcedureofInvestigation3FieldReconnaissance5MeticulousInvestigation41ObjectiveandProcedureofInvestigationDeepunderstandingofthegeologyatandbelowthesurfaceisneededforthesuccessfulandeconomicdesignandconstructionofcivilengineering,suchasrailway,expressway,etc.Theobjectiveofageologicinvestigationinvolvesthreeaspects,whichare:detailedknowledgeofthegeologicconditionrelatedtotheengineeringincludingtopographicfeatures,stratumandlithology,geologicstructure,hydrogeologicalcharacteristics,potentialmasswasting,specialsoils,meteorologicalfeatureandearthquakebackground,materialscanbeusedforengineeringworks;suitabilityevaluationofthesitefortheproposedengineeringworks;suggestionfordealingwiththegeologicconditionbasedonthesuitabilityevaluation.1.1ObjectiveofGeologicalInvestigation1.2ProcedureofGeologicalInvestigationThetypicalinvestigationforanimportantcivilengineeringproject,suchasrailwayorhighway,iscommonlyaccomplishedinthreestages,namelyanofficereconnaissance,afieldreconnaissanceandasiteexploration.Intheofficereconnaissancestage,availableinformationabouttheengineeringprojectandthegeologyofthelocationiscollectedandreviewed,basedonwhichreasonablefieldreconnaissanceplanandapreliminaryplanofthesiteexplorationareproposed.Inthefieldreconnaissancestage,theitemsincludebutarenotlimitedtotopographyandvegetation,surfacesoilandrock,naturalslopesandgully,geologicstructures,surfaceandsubsurfacewater,basedontheselectionwhichfinalplanofsiteexplorationisdecided.Inthesiteexplorationphase,someinformationischeckedandmadesurebytheuseofdrilling,samplingandgeophysicaltests.2OfficeReconnaissance1.DesignplansAdesignplanoratleastapreliminaryoneisalwaysavailableforanengineeringprojectbeforethefieldreconnaissancebegins.Thismayconsistofthecriterionoftheprojectandthelocationwheretheprojectwillbeconstructed.Theengineeringgeologistinchargeoftheinvestigationshouldbecomefamiliarwiththenatureofthestructuresandareastobeinvestigated.Inadesignplan,theexistingnearbysimilarprojectsarealwaysinvolvedandtheirinvestigationworksmaybedescribed.Theinvestigationresultsoftheexistingprojectsmaybeusedfortheknowledgeofthegeologicconditionoftheproposedproject.2OfficeReconnaissance2.EngineeringreportsEngineeringreportsmayprovidegeneralgeologyoftheexistingprojectsitesincludingrocks,soils,andgroundwaterconditionsthatarelikelytoprevailinthestudyareawheretheproposedprojectislocated.Areviewofformerconstructionsmayalsohelptoanticipategeologicalandgeotechnicalproblemsyieldingtheknowledgeofemphasesanddifficultiesoftheinvestigationofthestudyareafollowedbytheselectionofinvestigationmethods.2OfficeReconnaissance3.GeologicreportsandopenfilesAgeologyreportofanareaiscomposedofgeologicmaps,geology-relatedmapsandbriefdescriptionsofgeologicinformationmainlyincludingthestratum,rockandsoil,foldsandfaultsinthegraphicregionandtheirpossiblecausesofformation.Geologicreportsandopenfilesmayinclude:TopographicmapsGeologicmapsGeology-relatedmapsAerialphotographsPublishedpapersandarticles3FieldReconnaissanceAfieldreconnaissanceshouldcommencewithawalkoverthesitebasedonthesuggestionsfromtheofficereconnaissance.Theworkofthisstagehastwomajorpurposesregardlessofthesizeoftheengineeringproject:toobserveandanalysistheinformationthatwillaffectthedesignoftheprojectorthefollowingsiteexplorationplan;(2)tocollectandcompileinformationneededforthedrillcrewtocarryoutaboringprogram.3.1ItemstoObserve1ProposedlocationofprojectThelocationsofthebuildingsandstructuresproposedinthedesignplanshouldbeobservedonthegroundwiththehelpofatopographicmapandguidancefromlocalresidents.2TopographyandvegetationDuringfieldreconnaissancetheobservershouldwalkoverthetractoflandwhilestudyingthetopographicmapandobtaintheactualtopography.Vegetation,tosomeextent,indicatessurfacesoilsandgroundwaterconditions.3Surfacesoils,gullying,andnaturalslopesEluvium,deluvium,proluviumandalluviumshouldbeidentifiedinthefieldbyanalyzingthecharacteristicsoftheconstitutedparticlessuchasthedistributionofsizes,materialcomposition,andthedegreeofroundingandsorting,etc.Thedipdirectionanddipangleofthenaturalslopesshouldbemeasured.3.1ItemstoObserve4Surfaceandsubsurfacewaterswaterisaveryactive,sometimefatalfactorinfluencingtheshearingstrengthandcompressibilityofsoilandothergranularmaterials,whichmaydecidethestabilityofaslopeorthebearingcapacityofafoundation.Thepresenceofsurfaceorsubsurfacewaterisavaluableinformationinthedesignsoffoundation,cutslope,embankmentslopeandintheplanningofaboringplan.5GeologicstructuresThegeologicstructurecanbedeterminedthroughanalysisontherepetitionordeficiencyofthestratumandtheattitudes(strikeanddip)oftherockunitsasdetailedinchapter3oftextbook.Strikesanddipsofrockunitsandjointsshouldbemeasuredandnoted.3.2InformationNeededforDrillingWorkBeforethestartofthedrillingwork,thefollowinginformationisneeded:wheretodrill,howtogettothedrillingsite,whatpurposetoachieveandwhatparameterstoobtain,whatmethodtoadoptforthepurpose,whatequipmenttotake,isthereanyin-holemeasurement,andwhatpossiblechallengesmayoccurduringthedrilling.Generallythefollowingfactorsareinvolved:1Thefinalboringplan2Typeofequipment3Locationsofboringsandnearbyutilities4Permissionofpropertyowners5Otherinformation4SubsurfaceExplorationSubsurfaceexplorationcommencesafterthecompletionoffieldreconnaissancewiththefollowingtwopurposes:(1)tofindinterfacesbetweentwodifferentmediafollowedbythedeterminationofthedepthofsurfacesoiltobedrock,thedepthoftheslidingsurfacefromthegroundsurface,etc.and(2)toobtaincharacteristicsofsoilorrock,suchasroilandrocktype,bearingcapacityofafoundation,frictionalresistanceofsoilorrockatacertaindepth.Forthesepurposes,theexplorationmethodsaresubdividedgenerallyasfollows:(1)soundingofsoildepthtoreachrefusal,(2)drillingandsamplingofsoilandrockatvariousdepthsand(3)excavationoftestpitsinwhichinspectionandsamplingmaybeaccomplished.4.1MethodofDrilling1RotarydrillingSoilorrockiscutthroughbytherotatingofthedrillrodaroundthedrillaxis.Differenttypesofdrillbitsareusedaccordingtothevariousdrillingproposeandthepropertiesofthesoilorrock.Majorproceduresareusuallyusedinthisdrillingmethod,includingaugerboringwithsolidaugers,augerboringwithhollow-stemaugers,rotarydrillingwithrollerbits,androckorsoilcoring.Theseprocedureshavedifferentsuitabilityforsoils,rocksandgroundwaterconditionsfollowedbyvariouspossiblesamples.4.1MethodofDrilling2PercussiondrillingThistypeofdrillingismainlyusedinbedrockandgravellayers.Rocksarefracturedbythekineticenergyoftheimpactconefollowedbyadvancingahole.Thedrivingforceoftheimpactconecanbepneumatic,hydraulic,andgravity,ofwhichgravitydominates.Comparingwithrotarydrilling,percussiondrillinghashigher-performanceandlower-costingravellayersandweatheredbedrocksifwedonotcarethesampling.Despiteofthemineralogyandthecolordeterminationoftherocks,theholesareusuallymadebytheuseofthismethodforpurposesotherthanexploration.Theholesareusuallyusedforblastingholes,holesforgroutplacementandholesforbridgefoundation.4.2MethodofSamplingInalmostallinvestigationcases,samplesofsubsurfacesoilorrockorwaterarenecessarilyneededforlaboratorytestingtoevaluatetheinteractionbetweenthemandthestructuresbyobtainingtheirphysicalandmechanicalparameters.Samplescanbeclassifiedintodisturbedonesandundisturbedones.Disturbedsamplesarethoseinwhichthestructureofsampleshasbeenchangedduringthesamplingortransportation,andtheextentofthechangehassignificantlyaffectedsomepropertiesofthesoilorrock.Thiskindofsamplescanbeonlyusedfordescriptionandsoilclassificationandforlaboratorytestsinwhichtheeffectofstructureisnotimportant.Comparatively,undisturbedsamplesmaintaintheirstructureuntiltheyareusedfortesting,thatistosay,thechangeofthestructureissoslightthattheeffectonthenatureofthesoilorrockcanbeneglected.Undisturbedsamplesareusedalsoforthedeterminationsofnaturaldensity,naturalmoisturecontent,andtypeofsoilstructure;forevaluationsofshearingandcompressionstrengthofnaturalsoil;andforpermeabilityandconsolidationtestsofnaturalsoilandrock.4.2MethodofSampling1StandardpenetrationtestThistestisakindofdynamicpenetration,mainlyusedfordeterminingthebearingcapacityofsandorclayfoundation,alsoappliedfordisturbedsamplestakenbytheuseofasplit-spoonsamplerattachedtothedrillrod.Inthetest,thesplit-spoonsamplerispushedintothegroundbyaseriesofblowsfromthedrophammerhavingastandardweightof63.5kg(64kg/140lbinASTMD1568)withaheightoffallof760mm/30in.Thesamplerispushedinto150mmfromthedesigneddepthfollowedbythesubsequentthreeincrementsof300mmwiththenumberofblowsrecordedtoaccomplisheachincrement.Itisassumedthatthefirst150mmisusedtoseatthesamplerinthebottomoftheholeandthesubsequentthreeincrementsarethesignificantones.ThesumoftheblowcountsofthelastthreeincrementsiscalledSPTblowcountnotedasN,anditrepresentsthenumberofblowsper300mmwiththestandardequipment.4.2MethodofSampling2RotarycoringRotarycoringisthemostpopularmethodtoobtainacylindricalsampleofsoilandrockbyrotatingtheoutertubeofthesamplerwiththesampleslidingupinsideofthistube.Forconventionalrockcoring,drillrigsattachedwithdiamondbitsareusuallynecessarilyrequiredtoadvancethehole.Theinnerpartdoesnotrotateanditacceptsthecoreasthediamondbitsrotatesdownwardintotherock.Samplingefficiencyisaprominentprobleminthismethod.Whentheborebarrelisfull,theentiredrillstemhastobeliftedfromtheholetoobtaintherockcores.Inthisprocedure,alsocalledarun,thecorebarrelisbroughttothesurface,thecoreremoved,andthebarrelreturnedtothebottomofthehole.Thiscyclemaytakereasonablylongtimeiftheholeisfairydeepandthesoilmaycaveintotheholewhendrillinginproblematicsoilssuchaspebbles,gravels,loosesands,softclay.Corediscoveryisdefinedasthepercentageofcoreobtainedcomparedtothelengthoftheholedrilled.Closelyspacedrockfractures,weakrock,andchangesinlithologycontributetothecoreloss.Thedrillingequipmentandskillofthedrillermaybeals