Soil Mechanics in Engineering Practice.pdf

Soil Mechanics in Engineering Practice.pdf

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SoilMechanicsinEngineeringPracticeThirdEditionKarlTerzaghiLateProfessorofthePracticeofCivilEngineeringHarvardUniversityLecturerandResearchConsultantinCivilEngineeringUniversityofIllinoisRalphB.PeckProfessorofFotndationEngineering,EmeritusUniversityofIllinoisGholamrezaMesriProfessorofCivilEngineeringUniversityofIllinoisAWiley-IntersciencePublicationJOHNWILEY&SONS,INC.NewYorkChichesterBrisbaneTorontoSingaporeThistextisprintedonacid-freepaper.Copyright01996byJohnWiley&Sons,Inc.Allrightsreserved.PublishedsimultaneouslyinCanada.ReproductionortranslationofanypartofthisworkbeyondthatpermittedbySection107or108ofthe1976UnitedStatesCopyrightActwithoutthepermissionofthecopyrightownerisunlawful.RequestsforpermissionorfurtherinformationshouldbeaddressedtothePermissionsDepart-ment,JohnWiley&Sons,Inc.,605ThirdAvenue,NewYork,NY10158-0012.Thispublicationisdesignedtoprovideaccurateandauthoritativeinformationinregardtothesubjectmattercovered.Itissoldwiththeunderstandingthatthepublisherisnotengagedinrenderinglegal,accounting,orotherprofessionalservices.Iflegaladviceorotherexpertassistanceisrequired,theservicesofacompetentprofessionalpersonshouldbesought.LibraryofCongressCataloginginPublicationData:

Terzaghi,Karl,1883-1963.Soilmechanicsinengineeringpractice/KarlTerzaghi,RalphB.Peck,GholamrezaMesri.-3rded.p.cm.Includesindex.1.Soilmechanics.ISBN0-471-08658-4I.Peck,RalphB.（RalphBrazelton）11.Mesri,Gholamreza,1940-111.Title.TA710.T391995624.1513642095-6616PrintedintheUnitedStatesofAmericaIOToRuth,Marjorie,andLornaIn1948KarlTerzaghi,intheprefacetotheFirstEdi-tion,wrote:

Unfortunatelytheresearchactivitiesinsoilmechanics.divertedtheattentionofmanyinvestigatorsandteachersfromthemanifoldlimitationsimposedbynatureontheappli-cationofmathematicstoproblemsinearthworkengineering.Asaconsequence,moreandmoreemphasishasbeenplacedonrefinementsinsamplingandtestingandonthoseveryfewproblemsthatcanbesolvedwithaccuracy.Yet,accuratesolutionscanbeobtainedonlyifthesoilstrataarepracticallyhomogeneousandcontinuousinhorizontaldirections.Fur-thermore,sincetheinvestigationsleadingtoaccuratesolu-tionsinvolvehighlyspecializedmethodsofsamplingandtesting,theyarejustifiedonlyinexceptionalcases.Ontheoverwhelmingmajorityofjobsnomorethananapproximateforecastisneeded,andifsuchaforecastcannotbemadebysimplemeansitcannotbemadeatall.Ifitisnotpossibletomakeanapproximateforecast,thebehaviorofthesoilmustbeobservedduringconstruction,andthedesignmaysubsequentlyhavetobemodifiedinaccordancewiththefindings.Thesefactscannotbeignoredwithoutdefyingthepurposeofsoilmechanics.Theygovernthetreatmentofthesubjectinthisbook.Inthehalf-centurysincethesewordswerewritten,researchinsamplingandtestinghascontinuedunabated,andavastliteraturehasaccumulatedaboutthepropertiesofsoils,muchofitdirectedtowardadvancingoneoranotherschoolofthoughtconcerningidealizedconcep-tionsofsoilbehavior.Duringthesametime,remarkableadvancesinelectroniccalculationhavemadetheoreticalforecastspossibleforproblemsinvolvingcomplexboundaryandstratigraphicconditions.Thusitmaynolongerbetruethatifaforecastcannotbemadebysimplemeansitcannotbemadeatall.Inexchangeforthisprogress,however,ithasbecomeincreasinglyimportantthatthechoiceofsoilpropertiesusedintheanalysesbebasedonafundamentallycorrectknowledgeofsoilbehavior.PartIofthiseditionisessentiallyadigestofthefind-ingsofresearchworkersconcerningthepropertiesofsoilthatareofinteresttoengineers.Thedigestpresentsthefindingsfromafundamentalpointofviewratherthanasrepresentinganyoneschoolofthought.Becauseofthemanycontributionsoftheresearchworkers,thispartofthebookhasbeenexpandedmarkedlyoverthatofthepreviouseditions.Part11,ontheotherhand,hasbeenincreasedonlyslightly,becausetheessentialtheoreticaltoolswerealreadyavailable50yearsago.Thedevelopmentoffinite-elementandsimilarprocedures,althoughchangingthemodeofmanycalculations,hasnotalteredthisfact.Moreover,theclosed-formsolutionsoftheclassicaltheo-riesofelasticityandplasticitypermitthesimple,rapidapproximatecalculationsthatshouldalwaysbemadetoprovidea“backoftheenvelope”estimatetopermitjudg-ingtheneedfororthereasonablenessoftheresultsofanymoreelaboratecalculationalprocedure.Asinpreviouseditions,PartI11dealswiththeartofgettingsatisfactoryresultsinearthworkandfoundationengineeringatareasonablecost,inspiteofthecomplexityofthestructureofnaturalsoilformationsandinspiteoftheinevitablegapsinourknowledgeofthesoilcondi-tions.Thesemi-empiricalapproachdescribedandadvo-catedinthisParthasstoodthetestoftime.Ithasbecomethehallmarkofthepracticeofgeotechnicalengineering.TheauthorsareindebtedtoDr.M.T.Davisson,Mr.R.M.Armstrong,andProf.J.H.Longfortheirconstructivereviewsofthechaptersonpileandpierfoundations.ThepatientandexperttypingofthemanysuccessiveversionsofthetextbyMrs.PaulC.JesseandMrs.JoyceM.Snideraregratefullyacknowledged.ThenewillustrationsforthiseditionweredrawnbyMr.RonWinburn.Mr.MarawanShahienprovidedinvaluableassistanceincheckingthemanuscriptandinpreparing,revising,andsolvingtheproblems.Figuresandtablesfromjournals,proceedings,andbooksarereproducedwithpermissionfromtherespectivepublishers.RALPHB.PECKGHOLAMREZAMESRIxixPrefacetoFirstEditionSoilmechanicsoriginatedseveraldecadesagounderthepressureofnecessity.Asthepracticalproblemsinvolvingsoilsbroadenedinscope,theinadequacyofthescientifictoolsavailableforcopingwiththembecameincreasinglyapparent.EffortstoremedythesituationstartedalmostsimultaneouslyintheUnitedStatesandinEurope,andwithinashortperiodtheyproducedanimpressivearrayofusefulinformation.Theinitialsuccessesinthisfieldofappliedscienceweresoencouragingthatanewbranchofstructuralanaly-sisappearedtobeinthemaking.Asaconsequence,theextentandprofundityofthetheoreticalinvestigationsincreasedrapidly,andexperimentalmethodsweredevel-opedtoahighdegreeofrefinement.Withouttheresultsofthesepainstakinginvestigationsarationalapproachtotheproblemsofearthworkengineeringcouldnothavebeenattempted.Unfortunately,theresearchactivitiesinsoilmechanicshadoneundesirablepsychologicaleffect.Theydivertedtheattentionofmanyinvestigatorsandteachersfromthemanifoldlimitationsimposedbynatureontheapplicationofmathematicstoproblemsinearthworkengineering.Asaconsequence,moreandmoreemphasishasbeenplacedonrefinementsinsamplingandtestingandonthoseveryfewproblemsthatcanbesolvedwithaccuracy.Yet,accuratesolutionscanbeobtainedonlyifthesoilstrataarepracticallyhomogeneousandcontinuousinhorizontaldirections.Furthermore,sincetheinvestiga-tionsleadingtoaccuratesolutionsinvolvehighlyspecial-izedmethodsofsamplingandtesting,theyarejustifiedonlyinexceptionalcases.Ontheoverwhelmingmajorityofjobsnomorethananapproximateforecastisneeded,andifsuchaforecastcannotbemadebysimplemeansitcannotbemadeatall.Ifitisnotpossibletomakeanapproximateforecast,thebehaviorofthesoilmustbeobservedduringconstruction,andthedesignmaysubse-quentlyhavetobemodifiedinaccordancewiththefindings.Thesefactscannotbeignoredwithoutdefyingthepurposeofsoilmechanics.Theygovernthetreatmentofthesubjectinthisbook.PartAdealswiththephysicalpropertiesofsoilsandPartBwiththetheoriesofsoilmechanics.Thesetwopartsareveryshort,buttheycontainallthatengineeringstudentsandtheaverageengineerneedtoknowaboutsoilmechanicsproperatthepresenttime.TheheartofthebookisPartC.PartCdealswiththeartofgettingsatisfactoryresultsinearthworkandfoundationengineeringatareasonablecost,inspiteofthecomplexityofthestructureofnaturalsoilstrataandinspiteoftheinevitablegapsinourknowl-edgeofthesoilconditions.Toachievethisgoaltheengi-neermusttakeadvantageofallthemethodsandresourcesathisdisposal-experience,theory,andsoiltestingincluded.Yetalltheseresourcesareofnoavailunlesstheyareusedwithcarefuldiscrimination,becausealmosteverypracticalprobleminthisfieldcontainsatleastsomefeatureswithoutprecedent.EverydiscussionofpracticalproblemsinPartCstartswithacriticalsurveyofconventionalmethodsandpro-ceedsstepbysteptowhateverimprovementshavebeenrealizedwiththeassistanceoftheresultsofresearchinsoilmechanics.Therefore,theexperiencedengineerisadvisedtostartreadingthebookatthebeginningofthispart.HeshouldusePartsAandBonlyforreference,togetinformationaboutconceptswithwhichheisnotyetfamiliar.Otherwisehewouldbeobligedtodigestacon-siderableamountofmaterialbeforehewouldbeinapositiontorealizeitsfunctioninhisfieldofinterest.Thedetailsofthemethodsforcopyingwiththepracti-calproblemscoveredbyPartCmaychangeasexperienceincreases,andsomeofthemmaybecomeobsoleteinafewyearsbecausetheyarenomorethantemporaryexpedients.YetthemeritsofthesemiempiricalapproachadvocatedinPartCarebelievedtobeindependentoftime.AttheendofeacharticleofPartCthereaderwillfindalistofreferences.Intheirchoiceprioritywasgiventothosepublicationsthatarelikelytofostert