考虑固结路径影响的天然沉积土不排水剪切试验研究

针对传统等向固结剪切试验不能反映实际工程中的非等向变形和强度特性的局限,采用GDS应力路径三轴试验仪,对天然沉积结构性软黏土进行了不同固结条件下的不排水剪切试验,探讨不同应力路径对天然沉积土不排水剪切特性的影响.结果表明:相同的平均有效固结应力下土体偏压固结后剪切阶段应力-应变关系曲线的峰值强度大于等向固结的峰值强度;固结过程偏应力的存在提高了土体的总应力强度指标,当控制固结压力终值的剪应力相同时,偏压固结的强度包线相对于等向固结将平行上移;等向固结下当固结压力大于结构屈服压力时,有效应力路径与屈服面具有相似性,剪切屈服破坏后有效应力路径沿着临界状态线下滑;偏应力固结后剪切过程中有效应力路径的走向相对于等向固结发生了向右偏转.

Experimental study on undrained shear behavior of natural sedimentary clays under various consolidation stress paths

The conventional triaxial tests of isotropically consolidated undrained compression shear can not reflect the effects of anisotropic stress on the behavior of deformation and strength for natural clays which are often met in engineering practice.To solve the above problem,this study performed a series of GDS(geotechnical digital systems) consolidated undrained triaxial compression tests on natural clays subjected to the effects of soil structure under different consolidated conditions.The results indicate that the peak values of stress-strain curves obtained from triaxial anisortopically consolidated undrained shear tests are greater than those responsible for isotropic consolidation under the same mean effective consolidation stress.The total strength envelope obtained by triaxial anisotropically consolidated undrained shear tests lies above and parallel to that under isotropic condition,and the cohesive stress of total strength index increases due to the existence of the anisotropic stress.The effective stress path has a shape similar to the yielding surface when the consolidation stress reaches the order of the consolidation yield stress under the isotropic consolidations,and the effective stress path reaches the peak point at the critical state line and then slides down along it.The anisotropic stress causes the deflection of the effective stress path to the right with respect to isotropic consolidations.