适用于砂土循环加载分析的边界面塑性模型

基于临界状态土力学框架，建立了一个适用于砂土排水循环加载的边界面塑性模型。采用了考虑虚拟峰值应力比的偏应变硬化准则，初始加载阶段应力点位于边界面上，反向加载阶段以历史最大屈服面作为边界面，同时实现了对密砂软化现象的模拟和对历史所受最大应力的记忆。边界面采用修正的椭圆形，引入考虑密度与应力水平的状态相关剪胀函数，采用非相关联流动法则和以应力反向点作为映射中心的径向映射准则。模型仅有10个参数，通过常规三轴试验即可确定，并且使用一套参数可以模拟不同围压、密度的单调和循环加载情况。分别对饱和砂土的单调、循环排水三轴试验进行模拟，结果表明，该模型能够合理地反映饱和砂土排水条件下的应力-应变特性。

A bounding surface plasticity model of sand for cyclic loading analysis

A bounding surface plasticity model for describing the stress-strain behavior of saturated sand subjected to drained cyclic loading is presented within a critical-state framework. A hardening rule depending on incremental deviatoric strain is adopted. During the initial loading, the stress state always locates on the bounding surface. During the unloading and reloading processes, the bounding surface is the historical maximum yielding surface. This hardening rule can describe the softening phenomena of dense sands and remember the stress history by the bounding surface. The shape of the bounding surface is a modified ellipse, which enables the model to describe the plastic strain during loading with constant stress ratio. This model incorporates state-dependent dilatancy and adopts the non-associated flow rule, so it can reasonably describe the volume change behavior of sandy soil. A mapping rule passing through stress reversal points is adopted. A single set of 10 model constants calibrated by conventional triaxial tests is needed for one type of sand under different initial void ratios and different confining pressures. The predicted results by the model for the monotonic and cyclic triaxial tests on Hostun sand, Nevada sand, Toyoura sand and Fuji River sand demonstrate that the model can reasonably describe the stress-strain characteristics of saturated sand.