剪胀性砂土边界面模型的研究

剪胀性对于砂土,尤其是中密以及密实砂土,是一个非常显著的特性。相变线是剪胀性砂土的特征曲线,能够反映砂土的围压以及初时孔隙比对变形特性的影响。本文在边界面塑性理论的框架内,把相变状态参量引入到剪胀方程以及塑性硬化模量中,建立了一个能够描述砂土剪胀性以及循环特性的本构模型。本模型采用一套参量可以模拟不同初时孔隙比、不同围压、排水(或不排水)条件下单调(或循环)加载的应力-应变特性。验证表明本模型数值计算与试验结果相吻合。

A BOUNDING SURFACE PLASTICITY BASED CONSTITUTIVE MODEL FOR DILATANT SAND

One of the key issues in soil mechanics modeling is to correctly define the dilatancy function. Dense and medium dense sands dilate under drained conditions and develop negative excess pore water pressure when sheared under undrained conditions. A phase transformation line is present for dense and medium dense sand and characterizes the state from contractive to dilative. The phase transformation line is affected by the original void ratio and the effective confining pressure. In the proposed model, the state parameter which makes the phase transformation line as reference line is introduced into the stress-dilatancy equation. The plastic hardening modulus expression is used to develop a new dilatant constitutive model for sand within the general framework of bounding surface plasticity. The present model simulates, with a single set of model constants, both the contractive and the dilative responses of granular soils over a wide range of variations in stress and material internal states. The model can be used for both monotonic and cyclic loading paths under either drained or undrained conditions. It has been shown that the calculated results fit well with the test results.