砂土非共轴特性的本构模拟

Non-coaxial plasticity constitutive modeling of sands

传统的本构理论隐含了应力和塑性应变率的共轴条件,无法客观描述主应力轴旋转试验中的非共轴现象。因此,在已有的本构模型中引入非共轴塑性流动理论来描述这种非共轴现象,并对形状函数进行了修正。通过对真三轴试验、单剪试验和空心圆柱试验进行数值模拟,表明修正后的形状函数能够更好地描述砂土在真三维状态下的变形特性,更重要的是非共轴理论的引入使得模型能够合理预测主应力轴旋转过程中主应力和主应变率的方向变化规律。

The classical coaxial plasticity constitutive models implicate an inevitable limitation as directions for the principal stress and those for the principal plastic strain rate are always coaxial. They are not capable of simulating non-coaxial phenomena during the rotation of principal stress axis. A 3D non-coaxial plasticity constitutive model for sands with a modification of Lode angle dependent shape function is introduced to describe the non-coaxial behavior under the principal axes rotation. A series of numerical simulations of true triaxial, simple shear and hollow cylindrical torsional shear tests is performed. The results show that the proposed constitutive model can better describe the deformation characteristics of sand in true 3D state, and predict variations of the principal plastic strain rate directions with the principal stress directions reasonably.