Abstract: Degradation of saturated clay during cyclic loading can be assumed to be caused mainly by two mechanisms, pore water pressure build-up and the damage and remolding of soil fabric. Based on these mechanisms, a damage-dependent bounding surface model for cyclic degradation of saturated clay is proposed using the generalized isotropic hardening rule. In the model, the degree of damage and remolding of soil during cyclic loading is quantified by introducing a damage variable and the size of the bounding surface decreases with damage accumulation to characterize progressive degradation and nonlinear behavior of the saturated clay. By taking the stress reversal point as the generalized isotropic hardening center of the bounding surface as well as the mapping origin, the forms of hardening modulus can be adopted flexibly so as to predict the accumulation of plasticity deformation and pore pressure and the hysteresis property of clay. The cyclic behaviors for undrained one-way cyclic triaxial tests are predicted by the model. Moreover, the effects of the number of cycles, cyclic stress level and consolidation history on the cyclic degradation behaviors are analyzed. The agreement of predicted results with experimental data indicates that the model can realistically simulate the cyclic degradation behaviors of saturated clay.

Key words: cyclic loading, cyclic degradation, bounding surface model, generalized isotropic hardening rule, saturated clay