非饱和土水-力本构模型及其隐式积分算法

Implicit integration algorithm of a hydro-mechanical coupling constitutive model for unsaturated soils

在已有工作基础上建立了水力-力学耦合的非饱和土本构模型,在硬化方程中考虑饱和度的影响,同时在土水特征曲线中考虑了塑性体变的影响,从而使模型可以反映非饱和土中的毛细现象与土中弹塑性变形现象的耦合行为。采用隐式积分方法,建立了非饱和土耦合模型的数值模型,并推导了得到了水力-力学耦合的非饱和土的一致切线模量。利用该算法编制了本构模型计算的子程序,使其能向外输出切线刚度矩阵,用于有限元计算。为了验证该算法和程序的正确性,用所编制程序对不同路径下的土体行为进行了预测。通过预测结果与试验结果相对比,表明程序预测结果与试验数据相吻合,模型可以较好地模拟土体的水力-力学耦合行为特性。

A constitutive model for unsaturated soils？coupling of the mechanical behavior and hydraulic hysteresis is proposed. The degree of saturation is introduced into the hardening equation to reflect the hydraulic effect. Meanwhile, the plastic strain is introduced into the soil water characteristic curve to reflect the mechanical effect. Therefore, the model could well reproduce the influence of hydraulic behavior on the stress-strain behavior and vice visa. An implicit integration algorithm for integration of the nonlinear constitutive model is introduced. Consistent tangent matrix that describes the relationship between stress and strain and the one that describes the relationship between stress and suction are both derived. A corresponding program code is developed, which can be then embedded into existing finite element code for numerical simulation. In order to verify the correctness of the code, it is used to simulate existing test data under different loading paths including drying-wetting cycle test and triaxial shear test. Results indicate that the model accurately predicts the coupling effect of mechanical and hydraulic behaviors of unsaturated soils.