砂土三维多重机构边界面模型

以土的临界状态和边界面塑性理论为基础,引入状态参数,考虑砂土的剪胀特性,提出一个新型三维多重机构边界面模型。模型将复杂的宏观变形行为分解为一个宏观体应变机构和一系列空间分布的虚拟一维微观剪切机构。每个微观剪切机构包含一个微观剪应力–应变关系和一个微观应力–剪胀关系。利用三轴压缩试验中的应力条件,建立典型宏微观参数之间的关系。模型包含13个参数,多数可通过具有明确物理意义的土性参数来确定。通过对砂土三轴压缩试验和空心圆柱扭剪试验结果的数值模拟,表明模型不但能够合理反映在排水或不排水条件下砂土的硬化及软化特性,而且能在不增加任何参数条件下预测应力主轴旋转产生的变形累积特性和应变增量主轴与应力主轴之间的非共轴特性。

Three-dimensional multi-mechanism bounding surface model for sands

Within the multi-mechanism framework, a novel constitutive model for sands is proposed based on the critical state and bounding surface plasticity theories. The model assumes that the macroscopic deformation behavior of sands can be obtained by summation of the contributions from a macroscopic volumetric mechanism and a set of virtual one-dimensional microscopic shear mechanisms with random orientations in space. Each microscopic shear mechanism describes a shear deformation and a volumetric deformation due to dilatancy, which are modeled by both the microscopic shear stress-strain relationship based on the macroscopic bounding surface plasticity theory and the microscopic stress-dilatancy relationship, respectively. Both the strength criterion and the stress-dilatancy relationship introduce a state parameter for compatibility with the critical state theory. The correlations between some microscopic and macroscopic model parameters are formulated for the triaxial compression under constant confining stress. The model contains thirteen parameters and most of them are defined by soil parameters with the clear physical meanings. The systematic comparisons between the model simulations and the test data indicate that the proposed model has an excellent capability in predicting sand responses under the drained and undrained monotonic loadings, and the rotation of the principal stress axes without using additional parameters.