Nonlinear burgers model for sliding zone soil subjected to cyclic seepage pressure and its applications to the deformation analysis of landslide

Abstract

Numerous incidents and failures of bank slopes are caused by the creep behavior of sliding zone soil. During reservoir regulation, the pore water pressure in the sliding zone undergoes cyclic changes. Under such complex cyclic hydraulic conditions, the creep behavior may differ from that under the monotonic seepage condition, which is still poorly understood. In this paper, the Majiagou landslide in the Three Gorges Reservoir area is taken as a case study. Triaxial creep tests were first carried out to study the creep behavior of the sliding zone soil specimen under cyclic seepage pressure. Then, the nonlinear Burgers creep model was proposed to characterize the observed creep behavior of the sliding zone soil specimen, and the secondary development was performed based on FLAC3D software. Finally, the proposed model was applied to the Majiagou landslide to simulate its deformation under fluctuating reservoir water levels. The following results were obtained: (1) Under low deviatoric stress levels, cyclic seepage pressure causes the creep strain curve to fluctuate significantly. The decrease of seepage pressure leads to a reduction in pore pressure, resulting in a sharp increase in the strain rate of sliding zone soil. (2) The proposed model can well reflect the creep characteristics of sliding zone soil under cyclic seepage pressure. (3) During reservoir operation, the landslide deformation exhibits a step-like growth, and the proposed creep model can effectively simulate the retrogressive deformation characteristics of the Majiagou landslide. The research results provide the theoretical basis for the long-term stability of reservoir landslides under fluctuating water levels.