Abstract: An anisotropic bounding surface model for cohesive soils is developed based on Wheeler’s rotational hardening law (S-CLAY1 Model)，which is integrated in return mapping algorithm. The UMAT subroutine of the developed model is programmed in ABAQUS software. With the developed model, the numerical simulation of undrained triaxial compression test for normal consolidated kaolin clay (OCR =1) is implemented, and the numerical results of the developed model compared with the Modified Cam-clay model in ABAQUS. The results show that the developed anisotropic bounding surface model could efficiently depict the stress-strain behaviors and change of excess pore pressure of normally consolidated clay. Meanwhile the developed model could reproduce anisotropic behaviors of soft clay under loading conditions. Then the similar numerical simulation for over consolidated kaolin clay (OCR =4) is implemented. The results show that the developed model could also efficiently depict nonlinear stress-strain behaviors of over consolidated clay under small deformation conditions.

Key words: anisotropy bounding surface model for soil, return mapping algorithm, ABAQUS software, UMAT interface