三轴试验与应力路径.ppt

应力路径与三轴试验,路径：某物通过或移动的路线Path：Therouteorcoursealongwhichsomethingtravelsormoves。,应力路径：加载过程中应力点的轨迹。StressPath:Trajectoryofstresspointsduringloading.,应力路径表示方法,1）直角坐标系统2）直角坐标系统3）直角坐标系统4）直角坐标系统,三轴压缩试验（排水）,破坏线,三轴压缩试验（排水）,破坏线,破坏线,三轴压缩试验（排水）,Meannormalstress平均正应力Deviatoricstress偏应力,破坏线,三轴压缩试验（排水）,三轴试验的应力路径,三轴压缩（TriaxialCompression）三轴拉伸（TriaxialExtension）,排水试验（DrainedTest）不排水试验（UndrainedTest）,三轴试验,加载方式,排水条件,总应力路径（TotalStressPath）有效应力路径（EffectiveStressPath）,应力路径,三轴压缩（排水）,有效应力原理：,三轴压缩（不排水）,三轴拉伸（排水）,例题1,Aconsolidated-undrainedtriaxialtestonaspecimenofsaturatedclaywascarriedoutunderanall-roundpressureof600kN/m2.Consolidationtookplaceagainstabackpressure(反压力)of200kN/m2.Thefollowingresultswererecordedduringthetest.Drawthestresspaths,A(626.7,80),A(397.7,80),例题2,对一个砂土试样做三轴压缩试验，先在排水条件下对土样施加固结压力至200kN/m2。然后在不排水条件下增加三轴室的压力至350kN/m2。这时量测到的孔隙水压力u=144kN/m2。然后在不排水条件下增加轴向压力直到土样破坏。试验数据如下表。1.绘制偏应力和轴向应变的关系；2.在pq空间绘制总应力和有效应力路径；3.在st空间绘制破坏时的总应力和有效应力摩尔圆以及摩尔库伦强度包线，计算该砂土的剪切强度参数（内摩擦角）；5.确定孔隙水压力系数B的数值，绘制孔隙水压力系数A随轴向应变变化的关系，确定土样破坏时孔隙水压力系数A的数值。,相对于起点,相对于上一级荷载,各向异性固结Anisotropicconsolidation,Anisotropicconsolidation各向异性固结,k0consolidationk0固结,Nolateraldeformation,AnisotropicconsolidationandK0consolidation各向异性固结与K0固结,p,IsotropicConsolidationq/p=0,q,AnisotropicConsolidation(q/p=h0,K0Condition,nolateralstrain),AnisotropicConsolidationq/p=h,各向同性压缩,各向异性压缩,一维压缩k0压缩,材料：各向同性k1,Mohr-CoulombFailureEnvelopeinp-qSpace,Mohr-CoulombFailureEnvelopeinp-qSpace,SubstitutingEqs.2and3intoEq.1yields,(1),(2),(3),(4),Mohr-CoulombFailureEnvelopeinp-qSpace,RearrangeEq.4givesNoteheres1isthemajorprincipalstressands3istheminorprincipalstress.,Mohr-CoulombFailureEnvelopeinp-qSpace,Fortriaxialcompression,Therefore,wehaveSubstitutingEq.5intoEq.4resultsin,(5),(6),Mohr-CoulombFailureEnvelopeinp-qSpace,Fortriaxialextension,Therefore,wehaveSubstitutingEq.7intoEq.4resultsin,(7),(8),Mohr-CoulombFailureEnvelopeinp-qSpace,t,f,sa,c,sa,sr,s3f,s1f,s3f,s1f,sf(e),sf(c),tf(e),tf(c),s,TriaxialCompression三轴压缩,TriaxialExtension三轴拉伸,Mohr-CoulombFailureEnvelopeinp-qSpace,Therefore,theMohr-Coulombfailureenvelopeinthep-qspaceisasfollows,q,p,1,1,TC,TE,Mohr-CoulombFailureEnvelopeinp-qSpace,ThefailurestressratioM=|Dq/Dp|undertriaxialcompressionisdifferentfromthatundertriaxialextension:,Mohr-CoulombFailureEnvelopeinp-qSpace,Ifc=0(sandornormallyconsolidatedclay),thefailureenvelopeisasfollows:,q,p,1,1,例题,一个粘性土样本受一维压缩从O状态变化到A状态（如图所示）。在此一维原始压缩（virgincompression）过程中