Anisotropic UH model for soils based on a simple transformed stress method

A simple method, called anisotropic transformed stress (ATS) method, is proposed to develop failure criteria and constitutive models for anisotropic soils. In this method, stress components in different directions are modified differently in order to reflect the effect of anisotropy. It includes two steps of mapping of stress. First, a modified stress tensor is introduced which is a symmetric multiplication of stress tensor and fabric tensor. In the modified stress space, anisotropic soils can be treated to be isotropic. Second, a transformed stress tensor is derived from the modified stress tensor for the convenience of developing anisotropic constitutive models to account for the effect of intermediate principal stress. By replacing the ordinary stress tensor with the transformed stress tensor directly, the Unified Hardening (UH) model is extended to model the anisotropic deformation of soils. Anisotropic Lade’s criterion is adopted for shear yield and shear failure in the model. The form of the original model formulations remain unchanged and the model parameters are independent of the loading direction. Good agreement between the experimental results and predictions of the anisotropic UH model is observed