Experimental and numerical study of shear strength on the slide zone soil by the coupling of seepage and shear test

The stability of reservoir landslides is determined by the strength of the slide zone. Using both experimental and numerical techniques to analyze the strength of the slide zone has been widely used in the research of reservoir landslides. However, few models consider the strength of the coupling between seepage and shear. This paper aims to analyze the shear strength of slide zone soil combined with different stresses by using the directed shear test and particle flow code PFC^2D. The results indicated that slide zone soil clearly experienced the strain-hardening without seepage. While a specific strain-softening phenomenon was observed because the introduction of seepage reduced the shear strength significantly, the internal friction angle demonstrated a higher sensitivity to seepage stress compared to cohesion as the seepage stress increased. The direction and amount of flow velocity dynamically alter during the shear process, as revealed by numerical simulation results, suggesting that the shear strength was nonlinear with increasing seepage stress and changed structure. It can be assumed that seepage deterioration in the Huangtupo landslide is a dynamic process that influences the structure, strength and permeability characteristics.