双剪统一弹塑性应变软化本构模型研究

 根据统一强度理论应力不变量的形式，确定所要建立模型的屈服函数以及塑性势函数，考虑土体强度随加载过程的逐渐发挥，确定土体硬化函数。采用非相关联流动法则建立复杂应力状态下的土体弹塑性本构方程，并且对模型中所产生的奇异性进行分析和处理，指出模型中的奇异性是屈服函数、塑性势函数的流动矢量、以及硬化模量所引起的。给出模型中所含参数的确定方法，采用膨胀性泥岩的常规三轴试验模型进行验证，验证结果表明，所建立弹塑性本构模型能够模拟泥岩的应力–应变关系，较好地反映土体的应变软化特性。

TWIN SHEAR UNIFIED ELASTOPLASTIC CONSTITUTIVE MODEL CONSIDERING STRAIN SOFTENING BEHAVIOR

A yield function and a potential function were determined according to the twin shear unified strength theory. The hardening function of soils was established considering the development of soil strength during loading. An elastoplastic constitutive relationship under the complex stress state was proposed using the non-associated flow rule. The singularities in the constitutive model caused by the flow vectors of yield and potential functions and the hardening modulus were analyzed and resolved. The method of determining the parameters of the proposed model is presented. It was shown that the proposed constitutive model fit the strain softening curves from a conventional triaxial experiment of mudstone well.