结构性软黏土的修正剑桥模型

A MODIFIED CAM CLAY MODEL FOR STRUCTURED SOFT CALYS

天然软黏土普遍受到土结构性的影响,如何在土体本构模型中反映这一影响显得非常重要。该文从修正剑桥模型出发,引入结构屈服应力参数表征受土结构性影响的天然土初始屈服面的形状;引入各向异性参数描述天然土体初始各向异性引起的屈服面旋转。基于土结构性突变屈服破坏机理,屈服前结构性软黏土呈现弹性的力学性质,屈服后土结构性的影响完全丧失,采用同修正剑桥模型一致的硬化规律和流动法则。根据一致性连续条件,推导增量型的应力-应变关系,建立适用于结构性软黏土的弹塑性本构模型。选取国外已有的天然沉积Bothkennar软黏土,对比典型应力路径下的试验实测结果与模型计算结果,显示了该文模型模拟结构性软黏土受力变形特性的优越性。

Natural soft clays are generally subject to the effects of a soil structure. How to reflect the effects in the corresponding constitutive model is an important issue. Based on the modified cam clay model, a parameter designated as structure yield stress was introduced to describe the shape of an initial yield surface due to the soil structure, and an anisotropic parameter was presented to characterize the rotation of a yield surface due to initial anisotropy. According to the mechanism of abrupt loss of a soil structure for natural clays, the elastic stress strain relationship was applied in the pre-yield state, and corresponding hardening law and associated flow rule consistent with a modified cam-clay model were adopted since the resistance of a soil structure in the post-yield state is completely exhausted. According to the condition of consistency, the incremental stress-strain relationship was established and a modified Cam Clay model for structured soft clays was developed. Significant improvements were demonstrated in the performance of the new model by comparing with experimental data in the stress path tests for Bothkennar soft clay.