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Numerical study on the mechanical behavior of progressive failure of slope by 2D and 3D FEM

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Title

Numerical study on the mechanical behavior of progressive

failure of slope by 2D and 3D FEM( 内容の要旨(Summary) )

Author(s)

叶, 冠林

Report No.(Doctoral

Degree)

博士(工学) 甲第214号

Issue Date

2004-03-25

Type

博士論文

Version

URL

http://hdl.handle.net/20.500.12099/1935

※この資料の著作権は、各資料の著者・学協会・出版社等に帰属します。

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氏 名(本籍) 学 位 の 種 類 学位授与番号 学位授与日付 専 攻 学位論文題目 叶 冠 林(中国) 博 士(工学) 甲第 214 号 平成16 年 3 月 25 日 生産開発システム工学専攻 Numericalstudyonthemechanicalbehaviorl Slope by2D and3D FEM

(2次元,3次元FEMによる斜面の進行性破壊メ 究) 学位論文審査委員 (主査) (副査) 教 授 厚 太 鋒 真 嶋 戸 八 杉 張 授 授 授 教 教 教 助

論文内容の要旨

SlopefailureduetoheavyrainaIwaysdrawmuchattentionofgeo

becauseit maylead to tremendous disaster to human being andl dimculties to predict when and where the slope failurewi1loccI COnductedinthepaperareaimedtopredictwhenandwherearockslo]

The failure ofa soft-rOCk slopeis thoughtto belinkedwiths] excavation,CyClicdrylng-Wettingprocess,decreaseofe飽ctivestrez

negativeexcessiveporewaterpressure(negativeE.RWRinexcavatio】

E.RW巳).

Progressive Lhilure,Whichis a typICaltime-dependentbehavior;

fhilureofso氏rock・Indealingwithlong-termStabilityofaslope,tl behaviorsinso氏一rOCkgroundcanbeconsidered,thatis,theonecaus

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determination ofmaterialparameters,and above aIl,the time consumption ofcalcuJation・ Especiallyinthecaseconsideringthee能ctofthemovementofundergroundwater・Carefu1ground

surveylSneCeSSarytOaCqulreaSatisfhctoryaccuracyoftheanalysis・Furthermore,the2Dnnite elementanalysishasbeenusedtoevaluatethegeotechnicalproblemsforalongtimeandmany

experiences havebeenaccumulated・Therefore,nOrmalIyenglneerSPrefer2D analysisto3D analysistoevaluatethestabilityofaslope・

Tbevaluate the stability ofa slopein overconsolidated clay,Clay shale and soRrockby numericalsimu)ation,theconstitutivtmodelplaysamuchimportantrole・Someresearcheshave

beingdoneonso食sedimentaryrocks,bothinexperimentandnumericalmodeling・Itiscommonly

known that the mechanicalbehavior ofso氏sedimentary rockis elastoplastic,dilatant,Strain hardening-Strainso鮎ningatlowerconnningstresslevel,andtime-dependent・Thecementation

deteriorates because ofthe breakdown ofthe structure,Whichis usually caused by various processes,SuChaslargeshearlngdeformation,CyClicdrying-Wettingorstressrelaxation・The mechanicaIbehaviorofso氏rockduringshearlngislargelydependentonthecon坑ningstress,and alsothepore-WaterpreSSureWithintherock・

InChapter2,anelastoplasticstrain-SOfteningconstitutivemodelproposedbyOkaandAdachi

forso氏rockismodinedbyintroducingtheSMPfailurecriterionandthetijconceptinorderto

preciselytakeintoconsiderationthein飢1enCeOfin蔽hediateprlnCIPalstress・Themodelis

veri丘edbycomparlngthetheoreticalpredictionwiththeexperimentalresultsonanarti丘cialso氏

rock under plane-Strain condition・Itisfound that the modelcan describe not only the strain-SOtteningbehaviqrandstress-dilatancyrelationofso氏rockthatcouldbepredictedbythe originalmodel,butalsotheinnuenceoftheintermediateprlnCIPalstresstoasatisfhctoryaccuracy・ Itisalsoknown丘omthetheoreticaIpredictionconductedinthepaperthatdi飴rentfailurecriteria mayglVeatOtaldi飴rentstrain-hardeningandstrain-SO鮎ningbehaviorofageologlCmaterial・The materialparametersinvoIvedintheorlglnalmodelarealmostremainedthesameandonlyone parameterrelatedtostress-dilatancylSrePlacedbyadditionaltwoparameters,Whicharemuch easiertobedeterminedinconventionaltriaxialcompressiontests.Themodelcanalsobeappliedto

cohesivesoilsorsandysoilbychooslngaSuitablevalueoftheparameterみFurtherstudyshould

bedoneforthever描cationofthemodelundermoregeneralizedloadingconditions,forinstance,a truetriaxialsheartest. InChapter3,themathematicalfbrmulationsof2D,3D soil-WaterCOuPlingnniteelement

analysisareinducedbasedonBiot'stheory・Inthisformulation,nniteelementmethod(FEM)is

usedforthespatialdiscretizationortheequilibriumequation,Whilethennitedit粘rencemethod

(FDM)wasusedforthespatialdiscretizationofthepore-WaterPreSSureinthecontinuityequation・

TheninChapter4,basedonthemodinedelastoplasticmodel,2Dand3Dsoil-WaterCOuPled nniteelementanalysesareconductedtoinvestigateanactualprogressivefhilureofaslope,Which locatesatrrbkai-HokurikuExpressway,Japan・Theobservedhilureisatypicalprogressivehilure andtheheavyrainfhIlisthemainreasonforthehilure・Thecharacteristicsofslopefhilure,SuChas

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thedevelopmentofshearstrain,thedeformationofground,thepropagationofshearbandandthe progressivefhilureal・ediscussedil-detai1with2Dand3Danalyses・Thedifrbrencesbetween2D and3DanalysesarecareAJIIy)nVeStigated・ttisfbundthatboth2Dand3Dsoiトwatercoupled analysesbasedonthemodinedeJastoplasticmodelcansimulatetheprogressivefailureofas]ope・

InChapter5,amOdinedelasto-Viscoplasticmodelisproposedbyintroducingthe旬concept

andSMPfailurecriterionintothemodelprQPOSedbyAdachietaJ・・Thismodinedmodelcannot

onlydescribethestrainsoReningandtime-dependencybehaviorofsoftrockasorlglnalmbdel,but

alsotakeintoconsiderationtheinnuenceofintermediateprlnCipleitress.Basedonthemodined

and orlglnalelasto-Viscoplastic model,numericalanalyses are carried outtoinvestigate the

mechanicalbehaviorofaslopefailurelgnitedbytunnelexcavation・Ttisfoundthatbothmodels

can be adopted to simulate the progressive failure due to the time dependent property of geomaterial,althoughthereareslightlydi脆rencesbetweentwoanalyses・Furtherstudyshouldbe focusonthee飴ctoftheconstruCtionofretainingreclaimedsoiltothestabilityoftheslope・

論文審査結果の要旨

InthePhDcahdidate,sdissertation,nrStly;P3mOdinedelastoplasticmodelandamodi鮎d

elasto-Viscoplasticmodelwereproposed・Secondly,basedon theeIastoplasticmodels,2Dand3D soil-WaterCOuPled丘niteelementanalyseswereconductedtoinvestigatethemechanicalbehaviors ofaslopethilureduetoheavyrain・Atlast,2DFEAwasperformedtoanalyzeaslopefailuredue tothedeteriorationofsoilskeleton.Thenecessityofaccuratemodelsandthedi飴rencesbetween 2Dand3Danalysesare・Clarinedclearlyinthedissertation・Themainconclusions丘omthe candidate,sstudyarelistedbelow・ InChapter2,anelastoplasticstrain-SOReningconstitutivemodelproposedbyOkaandAdachi

forso氏rockwasmodinedbyintroducingtheSMPfailurecriterionandthe旬COnCePtinorderto

preciselytakeintoconsiderationtheinnuenceofintermediateprlnCIPalstress・Themodelwas verinedbycomparlngthetheoreticalpredictionwiththeexperimentalresultsonanartincialso氏

rock under plane-Strain condition・Itisfound that the modelcan describe not only the strain-SOfteningbehaviorandstress-dilatancyrelationofso氏rockthatcouldbepredictedbythe

orlglnalmodel,butalsotheinfluenceoftheintermediateprlnCIPalstresstoasatisfhctoryaccuracy・

ThematerialparametersinvoIvedintheorlglnalmodelarealmostremainedthesameandonlyone parameterrelatedtostress-dilatancylSrePlacedbyadditionaltwoparameters,Whicharemuch easiertobedeterminedinconventionaltriaxialcompressiontests・Asaconsequence,itispossible

toclarifythed騰rencebetween2Dand3Dnniteelementanalysesbasedonthemodel・

Tbsimulateaslope払ilureduetoheavyrainhIlorseverechangeofundergroundwater, soil-WaterCOuP]edana]ysISisnecessary・Therefore,inChapter3,fh・Stly,thefbrmulationsof2D& 3Dsoil-WaterCOuPlednnitee]ementmethodswerepresentrespective]y・Secondly・foraspecined

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boundal・yValueproblemconcernlngSOiI-Waterintel・aCtion,thetreatmentsofboundarycondition wereintroduced.Furthennore,tOaVOidtheinstabilityduringcalculationwhichadoptsthemodined model,SeVeralspecialtreatmentswereconductedinthe伽iteelementana]ys)S・ InChapter4,basedonasuitableelastoplasticmodeI,both2Dand3Dsoil-WaterCOuPled伽ite elementmethodswereconductedtorecoveraslopefailureduetoheavyrain・Itisfoundtheboth methodsareabletosimulatethetimedependentbehaViorofso氏rockduetosoilskeleton-POre waterinteraction,andtheprogressivefailureofarealslopeduetoheavyrainfhll・Thedetailed conclusionsobtained什omthecomparisonsof2Dand3DanalysescanbeglVenaSfo1lowlng‥

(1)Byadoptingasuitablee)astoplasticmodelforso代rock,both2D,and3Dsoil-WaterCOuPled

finiteelementmethodsareabletosimulatethetimedependentbehaviorofso氏rockduetosoil skeleton-POreWaterinteraction・AstheresuIt,theprogressivefailureofarealslopeduetoheavy

rainfa11canbesimulatedtoanengineeringacceptableaccuracy.(2)Fromthestress-Strainrelations

andthetimechangesofstrainrateinsoilelementsalongtheshearband,itisfoundthatthe formationandthepropagationoftheshearbandweredirectlycausedbythestrain-SOftening behavioroftheground・Comparedto2DanalysISlnWhichthepropagationoftheshearbandcan

onlydevelopln One Verticalplane,3D analysISis able to describethe propagationintwo orthogonalverticalplanes,beingmuchmorerealisticthan2Danalysisifcomparedwiththeneld

observation.In other words,3D analysiS Can glVe卑⊥甲Ore COmPrehensive description ofthe

progressivefailureofaslope.(3)An、overall鮎1ureofaslopewasignitedbythepropagationof

shearbandwithinthegroundofslope・Thisconclusioncanbeobtained-bothin2Dand3Danalyses・

(4)ThevolumetricexpansionofthesoiIwithinshearband,Obtainedftom2Danalysis,ismuch

sma11erthanthoseof3Danalysis・Consideringthefactorthatunderthesmallertheexpansionis, thesmaIlerthee能ctivecon伽ingstresswillbe,itisnotdifnculttounderstandtheresultthatthe groundat2Danalysisiseasiertofhilcomparedwith3Danalysis・Thatis,2DanalysISmayglVea

conservative estimation ofthe failure riskofaslope compared to3D

analysis・(5)Accurate

predictionofstress-dilatancyrelationwillplayaverylmPOrtantru1eindescribingtheprogressive

fhilureofasloperelatedtosoil-WaterCOupledproblem・(6)Presentanalysiscannotsimulatethe

processofmulti-StagePrOgreSSivefailureobservedintherealfhilureevent,thefailuresurfhce predictedby2Dand3Danalysescoihcidesonlywiththeobservedfailuresurfaceat伽alstage・

InChapter5,amOdinedelasto-Viscoplasticmodelwasproposedbyintroducingthetuconcept

andSMPfhilurecriterionintothemodelproposedbyAdachietal‥Theanalyticalresultsindicated thatthemodinedmodelnotonlycandescribethestrainsoReningandtime-dependencybehavior ofso氏rockasorlglnalmodel,butaIsocantakeintoconsiderationtheinnuenceofintermediate prlnCiplestress・Thenthemodelwasemployedinanumericalstudyonaslopefhilureduetothe deteriorationofground・Andtheresultswerecomparedwiththeonespredictedbyanalysisbased onorlglnalelasto-Viscoplasticmodel・Itiffbundthatbothmodelscanbeusedtosirnulatethe progressivefhilureduetotheinherentvisco-Plasticityofground,althoughtherewereslightly di脆rencesbetweentwoanalyses. Slopehiluremayleadtotremendousdisastertohtlmanbeingandcivlifhcilities,andhasbeen

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oneofthemostimportantanddi爪culttopicsingcotechincalresearch・Inthisstudy,thePhD candidateprovidedsomeusefu1methodstoanalyzetheprogressivehilureofslope,andobtained someveryexce11entconclusionsn・Omthenniteelementanalyses・Accordjngtothat,thecommittee approvedthatthisdissertationsatisneda11therequll・ementSfbrthePhDdegree・ ●

最終試験結果の要旨

八嶋

厚,杉戸

真太,本城

勇介および張

鋒で構成する審査委員会は,本論文およ

び論文別刷りなどを慎重に検討した.その結果,本論文は学位論文として十分に完成され

た内容を有していることを確認した.また,提出された査読論文は申請者によって書かれ

ていることを確認した.最終試験(公聴会)を平成16年2月10日に開催し,審査した.

審査委員会での審議の結果,合格と判定した.

参照

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