真三维应力状态下土体应变局部化的非共轴理论

Effect of non-coaxial plasticity on onset strain localization in soils under 3D stress condition

判别土体应变局部化的产生条件强烈依赖于土体塑性流动的非共轴特性。本文分析表明,由于传统的非共轴塑性理论是基于二维共轴应力空间得到的,为此,本文基于三维共轴应力空间建立了三维非共轴塑性理论框架,并利用三维非共轴塑性理论预测土体的变形分叉状态。数值模拟与试验结果对比分析表明,传统的本构模型有必要引入非共轴塑性流动理论才能有效地提高模型预测土体变形分叉特性的能力。研究表明:针对平面应变状态的变形分叉问题,由于考虑了应力第三不变量对非共轴性的影响,三维非共轴理论预测结果比二维非共轴理论更为合理。

The non-coaxiality＇of constitutive relationship has strongly influenced the predictions of the inception of strain localization for soils. It was shown that since the classical non-coaxial theory was built only on the basis of 2D coaxial strcss space, here an 3D non-coaxial constitutive framework was proposed based on 3D coaxial stress space and employed for predicting the onset of strain localization in soils. Comparisons between numerical predictions and experimental data were also provided. The analytical results presented that a non-coaxial plastic flow theory needed to be incorporated in the classical constitutive model to describe the bifurcation, which would lead to a correct prediction of the state of bifurcation. It was also concluded that the influence of the third stress invariant on the noncoaxiality, and that bifurcation analysis based on 3D model would get more precise results than 2D model under plane strain conditions.