中文摘要：

为合理模拟主应力轴旋转等复杂加载应力状态,对已有的结构性黏土的各向异性边界面模型中屈服面在π平面上的形状函数M（θ）进行修正,使其适用范围更加广泛,并将模型由三轴应力空间拓展到一般的三维应力空间。通过对天然沉积上海软黏土的一维压缩试验、等压及偏压固结三轴不排水剪切试验、一系列K0固结三轴排水应力路径试验以及不同中主应力系数和主应力轴旋转角度下的空心圆柱不排水剪切试验,对上海软黏土的屈服特性和主应力轴旋转效应进行了系统的研究。试验研究表明天然沉积的上海软黏土具有明显的结构屈服特性和塑性各向异性,初始状态边界面在p′q平面上呈并非以K0线为对称轴的倾斜椭圆形状,临界应力比随中主应力系数的增大而减小,验证了模型中所用的三维边界面方程的合理性;主应力轴旋转对天然沉积软黏土的应力应变关系及强度均有着重要的影响。通过天然沉积上海软黏土等压及偏压固结不排水三轴试验结果对模型参数进行标定,并对应力路径三轴排水试验以及主应力方向旋转的空心圆柱剪切试验结果进行计算,初步验证了拓展后模型在模拟复杂加载路径及主应力轴旋转效应的合理性和有效性。

英文摘要：

A three-dimensional structural anisotropic bounding surface model with a modified shape function of Lode angle is introduced to describe the effects of the principal stress rotation.One-dimensional consolidation tests and undrained triaxial tests under isotropic and anisotropic consolidation modes and a series of drained stress probe tests and hollow cylindrical undrained torsion shear tests with different coefficients of the intermediate principal stress are performed on natural undisturbed samples of Shanghai soft clay to study the yield characteristics and the effects of the principal stress rotation.The test results show that the properties of natural Shanghai soft clay are characterized by structural yield and anisotropic plasticity.The initial state bounding surface of Shanghai soft clay can be described by an inclined ellipse on the plane,and the limit state surface is not symmetrical as well with respect to the K0 line.The ratio of the critical stress decreases with the increase of coefficient of the intermediate principal stress.It shows that the equation of three-dimensional yield surface in the model is reasonable.Furthermore,the stress-strain relationship and strength of soft clay are influenced remarkably by the principal stress rotation.The parameters of the proposed model are calibrated by the undrained isotropic and anisotropic triaxial test results for natural Shanghai soft clay.The validity of the model is verified by drained stress path tests and hollow cylindrical torsion shear test results.Comparison between the simulated and experimental results shows that the effects of loading paths and the principal stress rotation are well captured by the model.