K_0固结软黏土的弹黏塑性本构模型

Elastic viscoplastic constitutive model for K_0-consolidated soft clays

在修正剑桥模型基础上综合考虑了软黏土的各向异性及率相关性,建立了适用于K0固结软黏土的弹黏塑性本构模型。模型借鉴过应力理论的基本思想,定义了与动态加载面相对应的参考屈服面,应用径向映射准则将两者联系起来,流动函数通过分析一维情况下土体的体积蠕变速率得到。以黏塑性体积应变为硬化参数,将一维情况扩展到三维应力状态,直接用次固结系数描述土体黏性强弱,所有参数可通过压缩试验及三轴不排水剪切试验得到。分别计算了代表性等向和K0固结黏土的三轴不排水等应变率加载、不排水剪切蠕变及蠕变破坏过程,与试验结果进行对比,验证本文模型的有效可行性。

A new anisotropic elastic viscoplastic （EVP） constitutive model was presented for K0-consolidated soft clays in general stress space. It was assumed that two surfaces existed for any loading history： dynamic loading surface and reference yield surface, both of them are nonsymmetrical ellipses with inclination defined by an α-line. The flow function was established by the visco-plastic volumetric strain rate under one-dimensional condition, the secondary compression coefficent was directly used to describe the rate effects. All model parameters could be easily gained from the results of one-dimensional compression tests and triaxial undrained shear tests. With the determined parameters, the anisotropic EVP model was used to simulate the behaviors of the triaxial undrained constant axial strain rate compression tests and undrained creep tests of some representative clays, it was demonstrated that the calculated results agreed with the test data well, and the present anisotropic EVP model was effective and feasible.