Elastoplastic modeling of cyclic behavior of natural structured clay with large number of cycles

Subgrade soils may be subjected to tens of thousands of traffic loading at a given stress level over a long period of time. Its long-term performance is therefore one of the major concerns of traffic geotechnical engineers. Up to now, it is still a challenge in constitutive modeling for describing the stress–strain responses with large number of cycles. For this, an elastoplastic model is proposed in this study to predict the undrained cyclic behavior of natural structured clay with large number of cycles. The proposed model includes three yield surfaces, an inner yield surface, an outer yield surface and an intrinsic yield surface. A hardening law associated with the inner yield surface is employed to computer the elaso-plastic transition inside the outer yield surface. Meanwhile, the elastic anisotropy, small-strain stiffness and structure degradation are considered in this model. In particular, a new hardening law of the inner yield surface which can flexibly control the hardening rate of the soil during cyclic loadings is adopted. Monotonic and cyclic (up to 50,000 cycles) undrained triaxial tests on Wenzhou clay are employed to verify the feasibility of the model. All comparisons demonstrate that the accumulative strains and pore water pressures during cyclic loadings are well captured by the model.