土体各向异性边界面模型隐式算法在ABAQUS软件中的实现

基于Wheeler土体各向异性旋转硬化法则，结合边界面理论，构造一个能够反映土体初始各向异性及加载后应力诱发各向异性的边界面本构模型，并借助ABAQUS软件提供的UMAT子程序接口，采用隐式积分算法--图形返回算法实现。通过对正常固结状态下（OCR=1）高岭土试样三轴不排水剪切试验进行模拟，并将模拟结果与ABAQUS自带的修正剑桥模型模拟结果进行了比较分析，表明本模型的模拟结果能够反映土体在偏压加载过程中产生的各向异性现象。在此基础上，采用本模型对中等超固结（OCR=4）高岭土试样三轴不排水剪切试验进行模拟，并再次与ABAQUS自带的修正剑桥模型模拟结果进行比较，表明本模型能够较好地反映中等超固结土在小应变情况下的非线性特性。相比于经典弹塑性模型，如修正剑桥模型，本模型的模拟结果更符合中等超固结土的变形特性。

On implicit integration of anisotropic bounding surface model for soils in ABAQUS software

An anisotropic bounding surface model for cohesive soils is developed based on Wheeler’s rotational hardening law(S-CLAY1 Model),which is integrated in return mapping algorithm.The UMAT subroutine of the developed model is programmed in ABAQUS software.With the developed model,the numerical simulation of undrained triaxial compression test for normal consolidated kaolin clay(OCR =1) is implemented,and the numerical results of the developed model compared with the Modified Cam-clay model in ABAQUS.The results show that the developed anisotropic bounding surface model could efficiently depict the stress-strain behaviors and change of excess pore pressure of normally consolidated clay.Meanwhile the developed model could reproduce anisotropic behaviors of soft clay under loading conditions.Then the similar numerical simulation for over consolidated kaolin clay(OCR =4) is implemented.The results show that the developed model could also efficiently depict nonlinear stress-strain behaviors of over consolidated clay under small deformation conditions.