Quantification of non-coaxiality in constitutive relationship of clays and its application to limit equilibrium problem

近年来，岩土材料的局部化变形问题引起了许多研究人员的关注，人们期望对土工材料的渐进破坏、地基尺寸效应等现象作出合理的解释。给出了饱和土体初边值问题的数学表达式，并在适当的初边值条件下，应用有限元技术进行了求解。土体骨架采用弹塑性凸轮粘土模型。在本研究中，将土/水耦合问题的理论框架推广到有限变形场，其中的初边值问题可能出现解的分叉。提出了控制方程的离散化方法。在检验了有限元格式的数值稳定性后，模拟了粘土试件在平面应变条件下的三轴压剪试验。结果表明，作为应变局部化的剪切带总是伴随着膨胀而发展的，这可称为膨胀局部化。此外，还对这种非线性土/水耦合公式在工程实践中的适用性进行了检验。

Recently, localized deformation in geo-materials has attracted many researchers with expecting rational explanation of phenomena such as progressive failure and size effect of footing on bearing capacity. The mathematical formulation of initial-boundary value problem for saturated soil mass is presented and the finite element technique is applied to solve it under appropriate initial and boundary conditions. The elastoplastic Cam-clay model is employed for the soil skeleton. In this study the theoretical framework for the soil/water coupled problem is extended to the finite deformation field where bifurcation of solutions in an initial boundary value problem may occur. The discretization for governing equations is proposed. After examining the numerical stability of the finite element scheme, the triaxial compression shear test of a clay specimen is simulated under the plane strain condition. It is revealed that the shear band observed as the strain localization in clay specimen always develops with dilation, which can be called the localization of dilatancy. Moreover is examined the applicability of such non-linear soil/water coupled formulation in the engineering practice in this study.