三维各向异性砂土UH模型

为了全面地描述砂土在三维空间不同方向上的本构特性，应当综合考虑各向异性和中主应力的影响。该文在砂土UH（统一硬化）模型的基础上，采用各向异性的变换应力方法，发展了三维各向异性砂土UH模型。该方法通过调整不同方向应力分量的相对大小，将各向异性砂土等效为各向同性砂土，并且在变换应力空间将偏平面上的破坏或屈服包线变成圆形。用各向异性的变换应力张量代替真实应力张量，能够方便地得到同时考虑各向异性和中主应力影响的砂土UH模型。与试验数据的对比表明，三维各向异性UH模型能够合理地预测真三轴应力状态下各向异性砂土的应力-应变关系。

THREE-DIMENSIONAL ANISOTROPIC UH MODEL FOR SANDS

In order to fully describe the stress-strain relations of sands along different directions in three-dimensional space, the effects of anisotropy and intermediate principal stress should be considered together. Based on the UH (unified hardening) model for sands, a three-dimensional anisotropic UH model is developed by introducing the anisotropic transformed stress method. In this method, magnitudes of the stress components along different directions are modified differently, so that the anisotropic sand can be equivalent to an isotropic sand, and the failure or yield curve in the deviatoric plane of the transformed stress space becomes a circle. If the stress tensor is replaced by the anisotropic transformed stress tensor, the UH model can be extended conveniently to consider the effects of anisotropy and intermediate principal stress. The comparisons with test results indicate that the three-dimensional anisotropic UH model can reasonably predict the stress-strain relations of anisotropic sands under a true triaxial stress state.