非共轴特性对岩土材料应变局部化行为影响的数值研究

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

基于传统连续介质力学的弹塑性本构模型默认主应力和主塑性应变率是共轴的,无法对土体分岔作出准确预测,同时由于其不包含任何内部长度参数,亦无法对剪切带的发展演化作出正确描述。为此,建立了一个基于微极理论的非共轴弹塑性本构模型,并编写了ABAQUS用户单元子程序(user-defined element,UEL),通过简单剪切实验验证了程序的正确性。通过平面应变压缩实验研究了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。

The principal stress and the principal plastic strain rate are co-axial by default in the elastic-plastic constitutive model based on the conventional continuum theory,which lead to the fact that the conbentional model cannot make precise prediction of the bifurcation of geomaterials.Meanwhile,no internal length scales are contained in the conventional model,which makes it cannot correctly describe the development of shear bands.Therefore,a non-coaxial elastic-plastic constructive model based on the Micro-polar theory was constructed in this study.The corresponding user-defined element(UEL)program was coded based on the software of ABQUS.The correctness of the program was firstly verified by a simple shear test.And then the effect of non-coaxiality on the onset,the thickness and the development of the shear bands were investigated through the plane strain compressive test.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.