Characteristics and failure mechanisms of rear reservoir-induced landslide-a case study of Shuiyunshan landslide in Xinshao, China

Abstract

The diversity of topographic and geological conditions significantly affects the kinematics and failure mechanisms of reservoir-induced landslides, especially those with rear reservoirs, which remain understudied. Taking the Shuiyunshan slow-moving landslide as a case study, this study investigates its failure mechanisms through a combination of field investigations, InSAR monitoring, and numerical simulations. The results reveal that the landslide is primarily driven by effective rainfall accumulation in a rear concave catchment area and sustained infiltration and erosion from rear reservoirs. The rear concave catchment area, which is 1.04 times the volume of the landslide body, alters the infiltration process of atmospheric rainfall. Approximately 61.9% of the rainfall generates surface runoff that accumulates in the rear reservoirs rather than discharging during rainstorms (100 mm/d). Furthermore, the distinctive geological structure featuring limestone interfacing with shale prolongs the infiltration process, while the rear reservoirs intensify groundwater recharge and weaken shale through prolonged immersion. The hydrostatic pressure and substantial hydraulic gradient exerted by the rear reservoirs significantly increase groundwater recharge within the landslide. Numerical simulations indicate that increasing the reservoir water level from 0 m to 3 m results in a decrease of approximately 16.3% in the safety factor of the most dangerous sliding surface of the landslide, highlighting the adverse impact of rear reservoirs on landslide stability. This study enhances the understanding of rear reservoir-induced landslides in mountainous regions, with implications for rural hydraulic infrastructure.