A novel seepage device and ring-shear test on slip zone soils of landslide in the Three Gorges Reservoir area

For the deformation and evaluation of reservoir accumulative landslide, it is of great significance to study the strength characteristics of slip zone soils under rainfall and reservoir operation. In this paper, slip zone soils from Tongjiaping landslide in the Three Gorges Reservoir area is taken as the research case, and the self-developed seepage device matching with the ring-shear test is designed and manufactured. Then, the shear strength of slip zone soils under different seepage-shear conditions is studied to reveal the strength evolution law of riverside landslide. Eventually, the creep characteristics of slip zone soils are described by the Burger model. The experimental results indicate that: (1) the weakening effect of slip zone soils will be induced by the increase of seepage cycles, change amount of seepage pressure, initial and constant seepage pressure, which decrease the residual strength of slip zone soils. (2) When the seepage cycles are <15, the weakening of residual strength of slip zone soils is not obvious. While when the cycles reach 20, the residual strength of soil samples decreases rapidly. (3) The Burger model, which connected the Maxwell model and Kelvin model in series can appropriately reflect the creep characteristics of slip zone soils of Tongjiaping landslide. The research results reveal the weakening law of mechanical strength of slip zone soils under seepage cycles, which provides a basis for the mechanism of accumulative landslide under the fluctuation of reservoir level.