基于能量耗散修正的Boom clay上下加载面模型及其数值实施

 针对剑桥模型不适用于超固结土和结构性土的局限性，引入上下加载面模型以描述Boom clay的结构性；基于Boom clay的屈服面的特点，通过修改能量耗散函数对上下加载面的形状进行了修正，构造了一个更好地反映其特性的弹塑性模型；以有限元程序ABAQUS的UMAT子程序接口为平台，采用隐式积分算法--最近点映射法(CPPM)实现了模型的二次开发；最后利用该模型对不同围压下的Boom clay 不排水三轴试验进行了模拟，并将该模型的计算结果与修正剑桥模型的计算结果以及试验实测结果进行了比较，结果表明，该模型能较好地反映Boom Clay在剪切过程中的结构性演化，且在一定程度上纠正了常规上下加载面模型高估重超固结土峰值强度而低估正常固结土和轻超固结土峰值强度的问题。

A MODIFIED SUPER-SUBLOADING SURFACE MODEL BASED ON ENERGY DISSIPATION FOR BOOM CLAY AND ITS NUMERICAL IMPLEMENTATION

Due to the limitation of Modified Cam-clay model，which can?t depict overconsolidated or structured clay，the concept of super-subloading surface was introduced to describe the destruction of Boom clay. According to the characterization of yield surface of Boom clay，the super-subloading surface model was modified based on energe dissipation. Adopting the closest point projection method(CPPM)，the UMAT subroutine of the developed model is implemented in FEM code ABAQUS. With the developed model and Modified Cam-clay model，numerical simulations of undrained triaxial compression tests on Boom clay under different confining pressure was performed. The simulated results with two different models were compared with the test results. It was shown that the developed model can depict the destruction process of Boom clay during shearing and the peak strength of overconsolidated clay was decreased compared with conventional super-sub loading surface model.