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1、摘要本文在修正劍橋模型的基礎上提出了一個物理意義明確、參數(shù)易于確定、計算比較簡單,并且能夠較為合理地模擬天然沉積土壓縮系數(shù)隨應力水平變化和各向異性導致屈服面傾斜的天然沉積軟粘土的彈塑性模型。論文的主要:l:作和創(chuàng)新點如下:1)基于天然沉積軟粘土的壓縮特性,提出了天然沉積軟粘_十的lnv—lnP’雙線性壓縮模型,建立了可以定量描述天然沉積軟粘土壓縮曲線的數(shù)學表達式,并采用對數(shù)應變形式,將目前被土力學模型廣泛應用的小變形彈塑性理論發(fā)展到有限變形理論之中,彌補了小變形彈塑性理論預測士體變形時的缺陷。2)提出結構性參數(shù)比來反映天然沉積軟粘七在受力過程中應力面的位置,描
2、述結構性喪失的過程。3)結合前人構建正常屈服面/結構屈服面二應力邊界面模型的思路,考慮硬化規(guī)則中塑性體積變形和剪切變形的共同影響,通過本文提出的雙線性壓縮模型給出了天然沉積軟粘土各向異性的有限變形硬化規(guī)律,提出一個考慮天然沉積軟粘土特性的彈塑性模型;4)選取了典型的江蘇連云港軟粘土和Bothkennar軟粘土為對象,通過與已有的試驗數(shù)據(jù)比較,驗證采用本文提出的天然沉積軟粘士模型進行模擬計算的合理性和有效性。關鍵詞:天然沉積軟粘土;雙線性壓縮模型;各向異性;本構關系;修正劍橋模型AbstractSoilstructureandanisotropyaretwoes
3、sentialfactorsforestablishingtheelasto—plasticconstitutivemodelfornaturallystructuredsoftclays.BasedOiltheModifiedCamClay,thisstudyproposesanewconstitutivemodelofnaturalsoftclaysthroughconsideringthechangeincompressibilitywithstresslevelandtheinitiallyinclinedyieldsurfaceduetoanisot
4、ropy.Basedonthebehaviourofnaturalsoftclaysunderone—dimensionalcompression,adouble-linecompressionmodelisproposedbyincorporatingthelinearrelationbetweenbothlogarithmsofthevolumeandmaineffectivepressure.Couplingwiththedouble-linecompressionmodel,adoubleinclinedyieldingsurface(normalyi
5、eldsurface/structureyieldsurface),ofwhichthemethodisoftenusedinthemulti—boundarysurfacemodel,isadoptedaswellasanewparameterCisproposedtodescribethedestructurationofthenaturalsoil.Consideringbothplasticvolumestainandplasticshearstainhardening,Thehardeningrulepertinenttotheanisotropyy
6、ieldsurfaceisproposedbasedonthedouble—linecompressionmodelinanaccuratefinitedeformationelasto—plastictheory,whichdoesn’thaveanyunrealisticpropertiesinthetraditioninducedbytheinfinitesimaldeformationeaisto—plastictheory.Significantimprovementsweredemonstratedintheperformanceofthenewm
7、odeloverthetraditionalconstitutivemodelsinthemodelingofmanyimportantfeaturesofthebehaviorofnaturalsoftclayswiththetriaxiaiexperimentaldataofLianYunGangsoftclaysandBothkennarclays.Keywords:naturalstructuredsoftclays;adouble—linecompressionmodel;anisotropy;ModifiedCamClayII東南大學學位論文獨創(chuàng)性
8、聲明本人聲明所呈交的學位論文是我個人在