考虑相变状态的较密实饱和砂土弹塑性模型

在三轴试验中，较密实砂土是很难最后到达临界状态的。该文在Yu等提出的CASM模型基础上，提出了适合模拟较密实饱和砂土的弹塑性模型。该模型有两方面的改进:一方面，模型将剪胀应力比M_d引入剪胀方程；另一方面，模型中硬化参数采用与应力路径无关的参数来替代CASM模型中的塑性体应变增量。经试验结果验证，该模型较适合模拟饱和中密或密实砂土的剪胀特性，同时也能较好地体现中密或密砂剪切过程中的硬化及软化现象。模型共10个参数，用常规三轴试验就可获取。

THE SATURATED DENSE SAND ELASTIC-PLASTIC MODEL CONSIDERING PHASE TRANSITION STATE

In the triaxial test, the dense sand is difficult to finally reach a critical state. Basing on Yu's CASM model, this paper presents an elastic-plastic model suitable to relatively dense saturated sand. The model has two aspects of improvements:firstly, the dilatancy stress ratio M_d is expressed by phase transformation state parameters, and it is introduced into a dilatancy equation; secondly, the parameters independent of stress path are used as hardening parameters to replace the plastic strain increment of a modified Cambridge model. Verified by some tests' results, the model is suitable to simulate the dilatancy of relatively dense saturated sand, and it can also reflect the hardening and softening characteristics during a shearing process. The model consists of 10 parameters that can be obtained directly from a conventional triaxial test.