How do spatial variations in soil-water characteristic curves control the local stability of landslide deposits?

Study region This study focuses on the Ma Zhongzui landslide, located in Jinyun Mountain, Beibei District, Chongqing, China, which has experienced secondary failure due to heavy rainfall. Study focus Soil hydraulic properties play an important role in rainfall3induced slope instability, especially the soil3water characteristic curve (SWCC). However, the SWCCs of landslide deposits exhibit heterogeneity, making it accurate assessment of the instability time and failure depth of these deposits challenging. This study emphasizes the impact of variations in SWCC parameters on the local stability of landslide deposits based on infiltration experiments and numerical simulations. New hydrological insights for the region The soil at the rear edge of the landslide deposit is relatively loose in structure, with a greater saturated conductivity ( k s ), air entry value parameter ( α ), and pore size distribution parameter ( n ), facilitating rapid pore water pressure ( PWP ) propagation under rainfall. Consequently, the rear edge to become unstable after 12.6 d, with a potential failure depth ( Z f ) reaching 2.32 m by the end of the rainfall. These values are significantly earlier and deeper than those observed at the middle (20.1 d, 1.74 m) and front edge (20.2 d, 1.72 m). Compared with predictions under homogeneous conditions, the instability time at the rear edge is significantly advanced, and Z f is increased by 26.1%. Slope stability is primarily influenced by the SWCC parameters α and n , and the effect of these parameters on Z f is nonlinear and constrained by rainfall amount. Z f is more sensitive to n when cumulative rainfall is less than 150 mm, whereas α becomes the dominant factor when rainfall exceeds 150 mm. This work holds significant value for precise early warning of the reactivation risks of landslide deposits in regions with abundant rainfall.