土体变形分叉的非共轴理论

Non-coaxiality for deformation bifurcation in soils

土体的变形分叉特性强烈依赖于土体的本构模型。由于传统的本构理论隐含了应力和塑性应变率的共轴条件,从而基于传统本构模型的变形分叉理论不能准确地预测土体变形分叉的失稳状态。由此引入本构模型的非共轴理论来分析土体变形分叉的失稳现象。通过与共轴的本构理论进行对比分析,研究结果表明,采用非共轴理论的本构模型能够合理地判别土体的失稳状态,理论预测剪切带的倾角随围压增大而减小的变化规律也与试验结果一致。

Predictions for the onset of deformation bifurcation are critically dependent upon the constitutive equations employed. The ordinary theory of plasticity stems from the considered flow rule, which is based on the assumption of coaxiality between the directions of principal plastic deformation rate and principal stress. Due to the major deficiency, the coaxial theoretical predictions cannot explain that the decrease of shear band inclination angle with increasing confining pressure and also underestimate shear strain of bifurcation. The inadequacy has led to the development of a consistent non-coaxial plasticity theory. The present analysis supports the hypothesis of non-coaxiality. Using this theory, the theoretical predictions for shear band orientation and its shear strain at the onset of bifurcation are shown to agree well with experimental observations.