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1、WhatistheFutureforSlopeStabilityAnalysis?(AreWeApproachingtheLimitsofLimitEquilibriumAnalyses?)Dr.DelwynG.FredlundUniversityofSaskatchewan,CanadaSecondSymposiumandShortCourseonUnsaturatedSoilsandEnvironmentalGeotechnicsBudapest,HungaryNovember4-5,2003IntroductionLimitE
2、quilibriummethodsofsliceshavebeen“Good”forthegeotechnicalengineeringprofessionsincethemethodshaveproducedfinancialbenefitEngineersareoftensurprisedattheresultstheyareabletoobtainfromLimitEquilibriummethodsSoWhyChange?ThereareFundamentalLimitationswithLimitEquilibriumMe
3、thodsofSlices??TheboundariesforaFREEBODYDIAGRAMarenotknown-TheSHAPEfortheslipsurfacemustbeassumedTheLOCATIONofthecriticalslipsurfacemustbefoundbyTRIALandERRORSHAPEandLOCATIONarethedrivingforceforaparadigmshiftObjectivesofthisPresentation:Toshowthegradualchangethatiseme
4、rginginthewaythatslopestabilityanalysescanbeundertakenToillustratethebenefitsassociatedwithimprovedproceduresfortheassessmentofstressesinaslopeOutlineofPresentationProvideabriefSummaryofcommonLimitEquilibriummethodsalongwiththeirlimitations(2-D&3-D)TaketheFIRSTstepforw
5、ardthroughuseofanindependentstressanalysisTaketheSECONDstepforwardthroughuseofOptimizationTechniquesIsaLimitEquilibriumAnalysisanUpperBoundorLowerBoundSolution?LimitEquilibriumMethodsprimarilysatisfytherequirementsofanupperboundtypeofsolutionReason:theshapeofslipsurfac
6、eisselectedbytheanalystandtherebyadisplacementboundaryconditionisimposedLimitEquilibriumandFiniteElementBasedMethodsofAnalysesWWWWWWWWNLimitEquilibriumMethodofAnalysisSm=tadldlsndlFiniteElementBasedMethodofAnalysisldtadlQUESTION:HowcantheNormalStressatthebaseofaslicebe
7、mostaccuratelycomputed?ConsidertheFreeBodyDiagramsusedtocalculatetheNormalStress?AssumptionforallLimitEquilibriumAnalysisSoilsbehaveasMohr-Coulombmaterials(i.e.,friction,f',andcohesion,c')Factorofsafety,Fs,forthecohesivecomponentisequaltothefactorofsafetyforthefriction
8、alcomponentFactorofsafetyisthesameforallslices()[]msnsSFuFc=-+bfsb'tan'SummaryofAvailableEquationsAssociatedwithaLimi
