非共轴特性对岩土材料应变局部化行为影响的数值研究

岩土材料的各向异性特征使其在主应力旋转的加载条件下出现主应力和主塑性应变率不共轴的现象,而传统的塑性流动理论默认两者是共轴的,导致无法正确预测应变局部化分叉的开始。另外,基于经典连续体理论的传统本构模型在模拟应变局部化边值问题时,由于没有任何内部长度参数,导致无法反映剪切带的宽度及发展演化。为此,本文建立了一个基于微极理论的非共轴弹塑性本构模型,研究岩土材料非共轴特性对剪切带的萌生、宽度和演化的影响,并与基于经典连续体理论的结果进行比较。发现基于微极理论的非共轴弹塑性模型不仅能够准确预测剪切带的萌生,而且能够很好地描述非共轴特性对剪切带宽度的影响。

Numerical Study of the Effect of Non-coaxiality on the Strain Localization of Geomaterials

The anisotropy of the geomaterials can cause the non-coaxiality of the principal stress and the principal plastic strain under certain loading condition. However, traditional plasticity flow theory implicitly assumes that the principal stress and the principal plastic strain rate are coaxial; thus, it may not correctly predict the onset of the shear band. In addition, classical continuum does not contain any internal length scales; as a result, it can neither describe the thickness nor the development of the shear band in the simulation of the boundary value problem. Therefore, a non-coaxial elastic-plastic constructive model based on the Micro-polar theory is constructed in this study. the effect of Non-coaxiality on the onset, the thickness and the development of the shear bands are investigated. The numerical results are compared with those obtained from the classical theory, which show that the proposed model can not only predict the onset of the shear band but also reflect the effect of the non-coaxiality on the thickness of the shear band.