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附二（1）翻譯英文原文PAGEPAGE33附錄二（1）翻譯英文原文AcasestudyofdamagesoftheKandlaPortandCustomsOfficetowersupportedonamat–pilefoundationinliquefiedsoilsunderthe2001BhujearthquakeabstractAcasestudyispresentedoftheinteractionbetweenthebendingduetolaterallyspreadingforcesandaxial-loadinducedsettlementonthepiledfoundationsoftheKandlaPortandCustomsTowerlocatedinKandlaPort,(a)liquefactionofthedeepsandysoilstratabelowtheclaylayer;(b)settlementofthegroundinthevicinityofthebuilding;(c)lateralspreadingofthenearbygroundtowardstheseafront.Thefoundationofthetowerconsistsof0.xxmthickconcretematand32piles.Thepilesare18mlongandthereforepassesthrough10mofclayeysoilandrestedonliquefiablesoils.Conventionalanalysisofasinglepileorapilegroup,withoutconsideringtheraftfoundationwouldpredictaseveretiltingand/orsettlementofthetowereventuallyleadingtoacompletecollapse.Ithasbeenconcludedthatthefoundationmatoverthenon-liquefiedcrustsharedaconsiderableamountofloadofthesuperstructureandresistedthecompletecollapseofthebuilding.CrownCopyright&2008PublishedbyElsevierLtd.Allrightsreserved.1.IntroductionFailuresand/orcollapse(excessivetilting)ofpile-supportedbuildingsinliquefiablesoilsarestillobservedaftermostmajorearthquakes,seeforexamplethereconnaissancesurveyfollowingthe1964Niigataearthquake,the199xxKobeearthquake,the2001Bhujearthquakeorthe2004Sumatraearthquake.Inmostofthecases,lateralspreading(downwardslopemovement)hasbeenconsideredtobethemaincauseoffailure[1–3,28],etc.Ithasbeenwell-recognisedthatlateralspreadingisamajorconcernforpilefoundationsinslopinggroundswhereathicknon-liquefiedsoillayeroverliesaliquefiedsoillayerandpilesareembeddedincompetentnon-liquefiablesoillayerbelowtheliquefiedsoil(seeCaseIinFig.1).Downslopemovementand/orlateralmovementofnon-liquefiedcrusthasthepotentialtoinducelargebendingmomentsinthepilesleadingtofailure.Thekindoffailureduetolateralspreadingisgenerallycategorizedasbendingfailureofpiles.Insomesituationswhentheshearcapacitiesofpilesareverylow,particularlyinhollowsections,lateralspreadingofsoilmaycausethepilestofailinshear.CaseICaseIICaseIIIFig.1.SchematicofapiledbuildinginliquefiedgroundCaseI:Lateralspreadingisthegoverningfailuremechanism,CaseII:BucklingisthegoverningfailuremechanismCaseIII:Settlementisthegoverningfailuremechanism.Ifinertiaeffectofthesuperstructureiscombinedwiththelateralspreadingforces,thepilesbecomemorevulnerabletobendingorshearfailure.Whenthetopnon-liquefiedsoillayerisabsent,dragforceexertedonthepilesbytheflowofliquefiedsoilisusuallyverysmall[4,xx].Insuchcases,ifthesoilliquefiestoadeeperdepth,thepilemaylosesignificantamountofthelateralstiffnessofferedbythesurroundingsoilandmaybehavelikeaslenderunsupportedcolumn.Iftheaxialloadactingonthepileishighenough,thisconditionmayleadtobucklinginstabilityofthepile[6,7](seeCaseIIofFig.1).Apiletransferstheaxialloadofthesuperstructuretothesupportingsoilintwoways:(a)sheargeneratedalongthesurfaceofthepileduetosoil–pilefriction,and(b)pointresistanceduetoendbearingatthebottomofthepile.Thissituationmayleadtothefailureofthefoundationduetoexcessivesettlement(CaseIIIofFig.1)renderingitunusableand/orexpensivetorehabilitatefollowingtheearthquakes.Ifthereissignificantdegradationofsoilstrengthduringearthquake,thesidefrictionandendbearingofpilesmaybecomeinsufficienttocarrythesuperstructureload.Itcanthereforebeconcludedthat,duringanearthquake,thepile-supportedstructuresinareasofpotentialsoilliquefactionmaycollapseduetostructuralfailureofpiles(i.e.,eitherbyshear,bendingorbuckling)orsoilfailure(i.e.,excessivesettlement).However,thesefailuremechanismsmayinteractwitheachother.Thispapersetsouttodemonstrateacasestudyoffailureofapile-supportedbuildingpossiblyduetotheinteractionbetweenaxial-loadinducedsettlementowingtoliquefactionandbendingduetolateralspreadingforces.ThebuildingisthePortandCustomsOfficeTowerofKandlaPort,whichissupportedonapiledraftandthattiltedduringthe2001Bhujearthquake.Athoroughgeotechnicalstudyofthesitehasbeencarriedoutandthefoundationsystemisanalysedconsideringthesoil–pileinteraction,effectoffoundationmatandnonlinearbehaviourofthesoil.Thismainintentionofthisstudyistoinvestigatetheplausiblecausesofthefailureofthebuilding.2.Acasestudy:tiltingofPortandCustoms2.1.TheearthquakeTheBhujearthquake(magnitude,Mw=7.7)thatstrucktheKutchareainGujaratat8.46a.m.(IST)onJanuary26,2001wasthemostdamagingearthquakeinIndiainthelastxx0years.Theepicenterofthequakewaslocatedat23.4N,70.28Eandatadepthof2xxkm,whichistothenorthofBacchautown.Thisearthquakehascausedextensivedamagetothelifeandproperty.EarthquakeSpectra[8]canbereferredfordetailedinformationabouttheearthquake.2.2.ThebuildinganditssiteKandla,locatedatthemouthoftheLittleRannofKachchhonthesoutheasterncoastoftheKachchhdistrict,isoneofthemajorseaport-cityofGujaratthatgotaffectedduring2001Bhujearthquake.Thisareaislocatedaboutxx0kmfromtheepicentreofthe2001Bhujearthquake.Manypile-supportedbuildings,warehousesandcargoberthsintheKandlaportareaweredamagedduringtheearthquake.Thepresentstudyanalysesthefailureofthe22mhighsix-floorbuildingcalledthePortandCustomsFig.2.LocationmapofPortandCustomstowerinKandlaPort.Thebuildingwasfoundedon32shortcast-in-placeconcretepilesandeachpilewas18mlong.Thepileswerepassingthrough10mofclayeycrustandthenterminatedinasandysoillayerbelow.Theultimatemomentandshearcapacityofthepileisestimatedtobe120–144kNmand4xx9–473kN,respectively(seeAppendix).Thetwovaluesofcapacityindicatethelowerandupperboundestimatesconsider-ingdifferentaxialloadsonpileduringseismicandserviceconditions,respectively.ThePortofKandlaisbuiltonnaturalgroundcomprisingrecentunconsolidateddepositsofinterbeddedclays,siltsandsands.Theverticalprofileoftheregionslopesdownwardsintheeasterlydirectiontowardsthecoastlineatabout12.Fig.3.ViewofnaturalgroundsonwhichtheportofKandlawasbuilt(Photo:EERI[8]).Thewatertableisabout1.2–3.0mbelowtheground.Fig.3showstheviewofthenaturalgroundsonwhichthePortofThetowerofthePortandCustomsofficeconsideredforthepresentcasestudyislocatedveryclosetoBerthsI–VoftheKandlaPort.ThetypicalboreholeprofileintheBerthI–Thesoilprofile(Fig.4)suggeststhattheuppersoillayersconsistofxx–10mthickdepositsofsoftsiltyclayunderlainbysandandhardclayminerals.Thesoilprofile(Fig.4)suggeststhattheuppersoillayersconsistofxx–10mthickdepositsofsoftsiltyclayunderlainbysandandhardclayminerals.Thesoilprofile(Fig.4)suggeststhattheuppersoillayersconsistofxx–10mthickdepositsofsoftsiltyclayunderlainbysandandhardclayminerals.Fig.4.TypicalsoilprofileinthevicinityoftowerofthePortandCustomsoffice.Thesoilprofile(Fig.4)suggeststhattheuppersoillayersconsistofxx–10mthickdepositsofsoftsiltyclayunderlainbysandandhardclayminerals.Thelowersoillayersconsistofyellowish-brownfineandcoarsesand,reddish-brownhardsiltyclaywithgypsum,andyellowish-browndenseclayeysand.Theuppersoillayershaveliquidandplasticlimitsrepresentativeofhighlyplasticclaysandhaveinsituwatercontentintherangeof42–47%.Thesoftsiltyclayhasliquidlimitintherangeof62–68%andplasticlimitbetween26%and28%withundrainedshearstrengthof10kPa(measuredfromvanesheartests).However,hardclayeysoilhasliquidlimitintherangeofxx4–77%andplasticlimitbetween39%and64%withundrainedstrengthof100kPa.Theinsituwatercontentofhardclayvariesfrom18%to27%.TheStandardPenetrationTest(SPT)‘‘N’’values(correctedforenergy)foruppersandylayersislessthan1xx,whiletheunderlyingdeepsandylayershaveSPTvaluesoflessthanxx0.Theinsitumoisturecontentofthesesandylayersvariesfrom10%to12.xx%.Theblowcounts(N?1xx–xx0)ofthesandylayerswithfinescontentbetween1%and32%indicatethatthesoilsarepotentiallyliquefiableunderstrongandsustainedshaking.2.3.Post-earthquakeobservationMostofthedamageatKandlaportareawasconfinedtobuildings,warehousesandcargoberthsoveranareaof2xx0m*60mlocatedinthecentralsectionofthePort.Thedamagetopilesupportedberthswerenotcriticalandtheoperationwasresumedontheberthsaftertemporarilyreducingtheworkingload.Ontheotherhand,thepile-supportedbuildingunderconsiderationleanedabout30cmatitstopandseparatedfromitsadjacentbuilding.Thegroundinthevicinityofthetowersettledabout30cm(onefoot),resultinginthesettlementoffloatingmatfloorsofthebuilding.Therewereevidencesofextensiveliquefactionwithejectionofsandthroughgroundcrackinthevicinityofthebuilding(seeFig.xx).Lateralspreadingwasobservedatthesite,however,noprecisemeasurementsareavailable.Fig.xx.DepositionofliquefiedsandthroughgroundcracksApost-earth-quakereconnaissancesurveyrevealedacontinuouspatternoflateralspreadingofmagnitude_80–100cminthevicinityofthebuildingsite(personalcommunicationwithProf.C.V.R.Murty,2008).Inthispaper,apredictionofthemagnitudeoflateralspreadingatthesiteiscarriedoutfollowingtheprobabilisticmethodproposedbyBrayandTravasarou[10].SomedetailsofthisanalysisarepresentedinSection3.3.Basedonthesurfacemeasurement,thepre-andpost-earth-quakeconfigurationofthebuildingisschematicallydrawninFig.6.Fromthesoil–pileconfiguration(Fig.6),withanassumptionthattherewasnostructuralfailureofthepiles,itcanbeinferredthatthepiletipcouldhavesettledabout4xxcm(30cmgroundsettlement+1xxcmbuildingsettlement)fromitsoriginalposition.3.EvaluationofseismicresponseofsoilsatthebuildingsiteAsthesoilprofilecomprisesofunconsolidateddepositsofinterbeddedclays,siltsandsands,itisquiteevidentthattheclayeysoilswillexhibitstiffnessdegradationandsandysoilswillundergoliquefactionduringstrongearthquakes.Thedegradationinstiffnessofclayeysoilsisafunctionofplasticityindex(PI),over-consolidationratioandmagnitudeofcyclicshearamplitude.Evaluatingtheseismicbehaviourofsaturatedsoils(sandorclay)requiresestimationofthestrainsorlossofstrengththatcancontributetogrounddeformationsorinstabilityduringorfollowingtheoccurrenceofanearthquake3.1.LiquefactionpotentialofsandysoilandcyclicfailurepotentialofclayeysoilInthepresentstudy,thepotentialforliquefactionofsandysoilshasbeenevaluatedbasedonthemethodrecommendedbyIdrissandBoulanger[11].Further,cyclicfailureinclayshasbeenevaluatedbasedonthenewprocedureproposedbyRef.[12].Theproposedmethodsaresemi-empiricalinnatureandareanextensionofmethoddevelopedbySeedandIdriss[13].Themethodisbasedontwoessentialcomponents:(a)back-analysingpastcasehistories;(b)useofplasticityindex(PI)torepresentthesoilbehaviourinto‘‘sand-like’’(PI<7)and‘‘clay-like’’(PI>7).Soilsexhibiting‘‘sand-like’’behaviourhavebeenevaluatedusingSPTmethodologyandthattheterm‘‘liquefaction’’isreservedforthesetypesofsoils.Further,soilsexhibiting‘‘clay-like’’behaviourhavebeenevaluatedusingtheproceduresappropriateforclays,andtheterm‘‘cyclicfailure’’isusedtodescribethefailureinthesetypesofsoils.Theseismicparametersrequiredintheanalysisarethemagnitudeofearthquake,i.e.,Mw=7.7,andthemaximumgroundaccelerationatthesite,i.e.,amax=0.33g.ThegeotechnicalparametersusedcanbereferredfromFig.4andTable1.TheresultsoftheanalysisfortheliquefactionpotentialandcyclicfailureswithdepthatthebuildinglocationarepresentedinFig.7.ItisevidentfromFig.7thatmostoftheclaystratumexceptthetop2mundergoescyclicfailureresultingingrounddeforma-tionandcracking.Furthermore,theentiresandystratumbetween10and22mislikelytohaveexperiencedliquefactionresultinginsettlementandflowfailure.Theaboveanalysisisconfinedtofreefieldconditionswithoutconsideringtheverticalstressesfromthebuildingloads.Ifverticalstressesduetothebuildingareconsidered,theneventhetop2mdepthofclaywillexperiencecyclicfailureresultinginsubstantialdeformationandcracking.Theaboveanalysissubstantiatestheobservationsthatliquefiedfinesandejectedtothegroundsurfacethroughthegroundcracksinthetopclaylayer.Therefore,theanalysesresultspresentedinthepaperareconsistentwiththefieldobservationsatthebuildingsite.3.2.SettlementofsoilSeveralfactorssuchasdensityofsand,maximumstraininducedinthesandandtheamountofexcessporepressuregeneratedbytheearthquakegovernthepostearthquakedensificationofsaturatedsands.Inthepresentstudy,twokindsofanalysishavebeencarriedouttoestimatethetotalsettlementofthesoildepositatthebuildinglocation.Thefirstanalysis(Method-1)isbasedontheapproachsuggestedbyTokimatsuandSeed[14].Themethodprovidesanestimateofpostliquefactionvolumetricstraininsaturatedsandsfromcyclicstressratio‘‘CSRM=7.xx”andstandardpenetrationresistance‘‘(N1)60’’.Thesettlementofeachlayerisgivenbytheproductofthevolumetricstrainandthelayerthickness.Thesecondanalysis(Method-2)isbasedontheapproachsuggestedbyIshiharaandYoshimine[1xx].Thisapproachprovidesanestimateofpost-liquefactionvolumetricstrainasafunctionofeitherthefactorofsafetyagainstliquefactionorthemaximumcyclicshearstrainandtherelativedensityorSPTresistance.Table2illustratesthesettlementanalysisforeachsandlayersofthesoilprofileandhencethetotalsettlement.Bothmethodsyieldalmostsimilarvaluesoftotalsettlementatthebuildingsite.Therefore,theseanalysesresultsareconsistentwiththeobservedsettlementofabout0.3m(onefoot)ofthenearbyground.Fig.6.PlausiblesettlementmechanismoffailureshowingthetiltingtheTower,assumingthereisnostructuralfailureofpiles.Thesiteresponseanalysisofthesoilprofilepresentedinthissectionpredictsliquefactionof12mofsandysoilbelowthe10mclayeycrust.Thismatchesquitewellwiththesurfaceobservationatsite.Theanalysisalsopredictsapost-liquefactionsettlementof0.31–0.37m,whichseemstobequitereasonablewiththeobservedgroundsettlementof0.3m.Hence,thisgivessomeconfidenceonthesoilprofilethathasbeenchosenforthestudy.3.3.LateralspreadingofthesoilPermanentgrounddisplacement,oftenreferredtoas‘‘lateralspreading’’infairlylevelgroundsisoneofthecriticalseismichazardsthatinfluencethestructuralresponse.Manyempiricalandsemi-empiricalproceduresareavailabletopredicttheamountoflateralspreading,seeforexampleNewmark[16],MakdisiandSeed[17],Finnetal.[18],AmbraseysandMenu[19],KramerandSmith[20],RathjeandBray[21],BrayandTravasarou[10].Inthepresentstudy,theamountoflateralspreadingatthebuildingsiteisestimatedusingthesimplifiedsemi-empiricalprobabilisticmethodproposedbyBrayandTravasarou[10].Forthisparticularsite,thecover-slidingmodel(i.e.,infiniteslopefailure)asdescribedbyBrayetal.[22]isappropriate.Thegroundisgentlyslopedandthereforethegroundslopeof1–xx1hasbeenused.Theamountoflateralspreadingatthesitehasbeenestimatedfortwocases:(a)probabilityofexceedanceof16%and(b)probabilityofexceedanceof84%.Eq.(1)hasbeenusedforthecalculations:whereDistheseismicdisplacement;kyistheyieldcoefficientofsoilslope(seeBrayetal.[22]forequationsforcalculatingky);Saisthepeakgroundacceleration;Tsistheinitialtimeperiodofthesoilcolumn?4H/Vs;Vsisthevelocityofshearwaveinthesoil;Misthemagnitudeofearthquake;andeisthestandarddeviationtakentobe0.66forthepresentstudy.Fig.7.Factorofsafetyagainstcyclicmobilityandliquefaction.andpercentagedegradationinstrengthofsoilduringearthquakefortheconsideredsoilpofile.WhileevaluatingtheexpressiongivenbyEq.(1),thefollowingvalueshavebeentaken:M?7.7,averageshearwavevelocityinthesoilmedium,Vs?200m/s,initialtimeperiodofground?Ts?4_10/200?0.2s,peakgroundacceleration=0.33g.Thevalueofkyisestimatedtobe0.0xx7and0.0xx4forthegroundslopeof11andxx1.Hence,theearthquake-inducedlateralspreadingisestimatedforthegroundslopeof11andxx1asgiveninTable3.Theestimatedvaluecomparesquitewellwiththepost-earthquakeobservationasdiscussedinSection2.1.Hence,forfurtherstructuralanalysis,lateralspreadingof1masanupperboundvaluewillbeused.4.ModellingofthefoundationsystemThefoundationsystemofthetowerconsistsofpilesandafoundationmat(seeFig.8).Theloadfromthesuperstructureissharedbetweenthepilesandthefoundationmat.Theinteractionbetweenfoundationsystemandthesoilisrepresentedbysetsofnonlinearspringsandisdetailedlaterinthispaper.Inthepresentstudy,thesuperstructureloadiscalculatedandappliedonthefoundationmatatthelocationsofthecolumns.Theestimationofsuperstructureloadandthenumericalmodelusedforthepresentstudyaredescribedinthefollowingsection.4.1.LoadcalculationTheloadsfromsuperstructurearetransferredtothepilesthroughthefoundationmat,whicheventuallyactslikeapilecap.Fig.8showsthemajordetailsofthebuilding.Theserviceloadofthebuildingisestimatedtobe10,749kN(Table4).Assumingequalsharingoftheverticalloading,thestaticaxialloadperpileisapproximately336kN.Theanalysispresentedinthepaperisbasedonthisstaticaxialloadonthepile.Thedynamiceffectsareignored.4.2.ModellingofpilesandfoundationmatThecastinplaceconcretepilesaremodeledascolumnwithspecifiedaxialandlateralstiffness.Foundationmatismodeledasthickslabwithacut-outof4.7m_7.7matoneside(seeFig.8).Inthepresentanalysis,thefoundationmatandthepilesaretreatedaslinearelasticconcreteelementsasnonlinearbehaviourofthematerialisnotexpected.However,thenonlinearityofthesoilisincorporatedintheanalysis,whichwillbedescribedinthefollowingsections.4.3.ModellingofsoilSoilishighlynonlinearwhensubjectedtolargedeformationanditstiffnessalsovarieswithdepth.Thebehaviourofpilefoundationsubjectedtoseismicloadinggreatlydependsonthesoil-pileinteraction.Severalanalyticalandsemi-empiricalmeth-odshavebeenusedinpracticetomodelthesoil–pileinteractionincluding:(a)continuummodel,(b)numericalfiniteelementmodel,and(c)Winklerspringmodel.Winklerspringmodelisextensivelyusedinpracticeduetoitssimplicity,mathematicalconvenienceandabilitytoincorporatenonlinearity.Fig.8.MajordetailsoftheKandlaPortandCustomsOfficeInthepresentstudy,thesoilinteractingwiththefoundationofthebuildingisrepresentedbyWinklersprings.Fourtypesofsoilsprings(Winklertype)areusedinthepresentanalysis(seeFig.9)suchas:(a)Axialsoilsprings(t–zsprings):torepresentsoilresistanceatpilesurfacealongitslength,(b)Lateralsoilsprings(p–ysprings):torepresentthelateralresistanceofsoiltothepiles,(c)Endbearingsprings(q–zsprings):torepresenttheendbearingofsoilatthebottomofthepiles,and(d)Shallowfoundationbearingsprings(Q–usprings):torepresenttheresistanceofthesoilunderthefoundationmattoverticalsettlementofthemat.Theload–deflectioncurvesforthepilesprings,i.e.,firstthreetypesofspringsfornon-seismicstateareestimatedbasedonAPIguidelines.However,itisunderstoodthatwhilesubjectedtostrongseismicshaking,saturatedclayeysoillosesitsstrengthduetocyclicmobilityandsaturatedsandysoillosesitsstrengthduetotheincreaseinporewaterpressure.Thepresentstudyrequiresthedegradedstrengthofsoilwhileanalyzingfortheseismiccondition.Forclayeysoil,analysisiscarriedoutinSHAKEtodeterminethereductioninitsstrengthduetoseismicshakingwithaPGAof0.33g.Thedegradedstrengthofsandysoilatliquefactionistakenas10%ofthestrengthofnon-liquefiedsandassuggestedbyAIJ[23]code.Thestrengthofsoilatvariousdepthsbeforeandduringtheearthquake(i.e.,serviceandseismicconditions)ispresentedinTablexx.Thenonlinearload–deflectioncurvesforthespringsareshowninFig.10.Forshallowfoundationbearingsprings,theinitialstiffnessiscalculatedusingtheEq.(2)asfollows:(2)Wherea,barethewidthandlengthoftheraft,GistheshearmodulusofsoilandristhePoisson’sratio.Theultimateload-carryingcapacityunderthemat(Qu)iscalculatedbyusingEq.(3),consideringtwo-layersoilapproach,wheretheclayeycrustisconsideredtooverlayontheliquefiedsand:(3)Fig.9.Schematicshowingvariouspartsofthefoundationsystemconsideredinthepresentstudy.WhereSuistheundrainedstrengthofthesoil,andNcisthebearingcapacityfactorfortwo-layeredsoil[24].Thedegradedsoilstrengthfactor(b)at0.xxmdepthfromthegroundisabout80%(Fig.7).Hencethestrengthofsoilunderthematduringearthquakeistakenas80%ofthestrengthofsoilduringservicecondition(seeTablexx).xx.Analysisofasinglepilexx.1.SettlementanalysisAxialloadtransfer(t–z)analysisiscarriedoutforasinglepiletostudythesettlementcharacteristicofthetowerduringreducedsoilstiffness.Thepileisconsideredasacolumnwithspecifiedaxialstiffnessanddiscretisedinto18elementsof1mlength.ThesupportingsoilismodeledasWinklerspringsasshowninFig.11.Twotypesofspringsareconsidered:(a)axialsoilspringrepresentingthesidefriction(t–zspring)and(b)end-bearingspring(q–zspring).Thenetsettlementofpileundertheactionofaxialloadcanbeconsideredtobeanalgebraicsumofthreecomponents:(a)axialcompressionofthepile,(b)slipbetweensoilandpileinterface,i.e.,mobilizationofthesideresistanceand(c)settlementofthesoilmassasawhole.Aniterativecalculationiscarriedouttoestimatethepilesettlementasmobilizationofthesideresistancedependingontheslippagebetweenthepileandthesoil.Theanalysisiscarriedoutfortwoconditions:(a)serviceconditionand(b)seismiccondition.Inservicecondition,theloadingoneachpileisconsideredtobe336kNandthesoilspringsareestimatedbasedonthesoilpropertiesbeforetheearthquake.Forseismiccondition,thepileloadistakenthesameignoringthedynamiceffectonaxialload.ThesoilspringsaredegradedforseismicconditionasgiveninTablexx.Fig.12showstheaxialloaddistributionalongthelengthofthepileunderserviceconditionsaswellasseismiccondition.Foreachoftheconditions,maximumloadcarryingcapacityofthepilebasedongeotechnicalconditionsisalsoplotted.Theaxialloadcarryingcapacityofthefoundationwas1260kNbeforeearthquakeandtheaxialloaddemandonthepilewas336kN.Asexpected,theaxialcapacityofthepilereducedsignificantlyduringtheseismiceventduetoreductionofthesoilstrength.CalculationshowsthattheaverageaxialloaddemandofthepileFig.10.Load–displacementcurveforsoilspringsofclayeyandsandysoil.of336kNismorethanthemaximumaxialloadcarryingcapacityofthepileof1xx6kNduringseismiccondition.Thisimpliesthattheresistanceofferedbysurroundingsoilbysidefrictionandendbearingisnotadequatetocarrytheappliedaxialload.Thisconditioninturnwillleadtocompletebearingfailureofthepileintothesoil.However,thisdoesnotmatchwiththeobservedbehaviourofbuildingfailure.Therefore,itisconsideredplausiblethattheraftisbearingapartofthesuperstructureload,asthepileandtheraftactsasanintegralsystem.xx.2.LateralspreadinganalysisThisanalysisiscarriedouttostudythebehaviorofthepilesofthebuildingwhilesubjectedtolateralspreading.Thereweresomeevidencesofliquefactioninducedlateralspreadingatthebuildingsiteasdescribedinprevioussectionsofthispaper.Thepileswereembeddedinanon-liquefiableclayeycrustandterminatedinaliquefiedsoillayer(seeFig.13(a)).Intheeventoflateralspreading,thetopnon-liquefiedclayeycrustwilldisplacelaterally.Itcanbeexpectedthatthetop10mofclayeylayerwilldisplaceasawholealongwiththebuilding.Atriangularvariationofthegrounddisplacementcanreasonablybeassumedforthe8.xxmofliquefiedsoillayer.Fig.13(b)showsaplausiblepatternofsoilmovement.Thebuildingwillthereforebedisplacedlaterallythesamedistanceastheclayeysoil(i.e.,dg?topclaycrustmovement?movementofwholebuilding?1m),asarigidmassmovement.Thebottompartofthepile,ontheotherhand,willbeexposedtotheliquefiablesoil,andwillbesubjectedtoreverseforceduetorelativesoil–pilemovement(seeFig.13(c)).Theresponseofpilesubjectedtolateralspreadingcanbeestimatedbyusingeitherdisplacement-orforce-basedanalysis.Ascomparedwiththedisplacementbasedanalysis,theforce-basedanalysisiseasytodoandcanevenbecarriedoutwithsimplehandcalculations.Therearevariousmethodsavailabletoquantifytheforceonthepileduetotherelativemovementofliquefiedsoil.Fig.11.Analyticalmodelforsettlementanalysisofasinglepile.Fig.12.Resultofsettlementanalysisofasinglepile:(a)serviceconditionand(b)seismiccondition.JRAguidel