Abstract: A fully implicit integration scheme in the bounding-surface plasticity model for cyclic behaviors of saturated clay is presented by modifying the conventional implicit return mapping algorithm. Within the critical state framework, based on the concept of shrinking the elastic region to a point, combining isotropic with kinematic hardening rule and a rotated bounding surface, and introducing a damage parameter representing the remolding of the soil fabric, the model can reflect the initial anisotropy, the cyclic stiffness degradation and strength softening of saturated clay under cyclic loading. Firstly, the numerical simulations of the undrained triaxial tests both for isotropic ( ) and anisotropic ( ) consolidated kaolin clay are carried out with variable strain increments. By comparing with the test data, the rationality, robustness and the accuracy of the new fully implicit integration for the bounding surface plasticity model are verified. Furthermore, the prediction for an undrained cyclic triaxial test on a saturated clay is given, and the cyclic degradation of the stiffness and strength is obtained, which indicates the validity of the computational results.

Key words: bounding-surface plasticity model, implicit return mapping algorithm, cyclic behaviors, saturated clay