Dynamic stability assessment of reservoir colluvial landslide using a hypoplastic clay constitutive model considering the effects of drying-wetting cycles on the hydro-fluctuation belt

Abstract

The hydro-fluctuation belt of reservoir landslides undergoes repeated drying-wetting (D–W) cycles due to the annual fluctuation of water level in the Three Gorges Reservoir Area. Mechanical properties of the hydro-fluctuation belt subjected to D-W cycles should be considered for the evolution of landslide stability affected by seasonal rainfall and periodic reservoir water fluctuations. In addition, a reliable constitutive model essential for evaluating landslide stability should be employed to describe the mechanical property of soil. In this study, taking the Tangjiao landslide as an example, a series of drained triaxial and oedometer tests were conducted to study the effects of D-W cycles on the shearing and compression behaviors of the sliding mass soil. Then, the time-varying parameters of a hypoplastic clay constitutive model were calibrated based on the soil experiments under different D-W cycles. Eventually, the hydro-mechanical coupled simulation analyses were performed to study long-term deformations of the landslide front part influenced by actual rainfall and reservoir water fluctuations. Moreover, the evolution of landslide stability was analyzed using the vector-sum method based on stress fields with different time steps. The test results show that the D-W cycle significantly affects the mechanical property of soil. The hypoplastic model predicts well the shearing and compression behaviors of soil under different D-W cycles. The numerical results indicate that the soil weakening in the hydro-fluctuation belt increases the deformation magnitude of the toe slope and gradually decreases the landslide stability. This study provides some references for the dynamic stability assessment and long-term hydro-mechanical simulation of reservoir landslides.