Typhoon-induced rainstorms frequently trigger numerous landslides, among which slow-moving landslides are typically large in scale and highly destructive. Elucidating the deformation characteristics and genesis mechanisms of landslides under typhoon rainstorm conditions is of great significance for landslide monitoring, early warning, and risk mitigation during typhoon events. In this study, a typhoon rainstorm-induced landslide in Zhonglin Village, Zhejiang Province, China, is taken as a case study. A combined approach integrating finite element numerical simulation and physical model testing was employed to investigate the evolution of the transient groundwater seepage field and the stability response of the landslide under two rainfall scenarios: constant-intensity rainfall with a maximum daily rainfall of 200 mm/d and gradually varying-intensity rainfall.
The results indicate that the deformation and failure process of typhoon rainstorm-induced landslides can be divided into two distinct stages: a disaster incubation stage and a failure stage. Rainfall during the pre-typhoon period corresponds to the incubation stage, during which landslide displacement remains small and the slope is characterized by slow creep. Tensile and shear cracks develop on the slope surface, the sliding surface is relatively shallow, and the dominant instability mode is creep-tensile cracking. In contrast, extreme rainstorms during the typhoon period represent the failure stage. Intense rainfall markedly enhances groundwater runoff intensity and flow velocity, resulting in soil and rock particle loss and the formation of subsurface voids. These processes trigger collapse of the upper slope mass, large-displacement sliding, and the development of arc-shaped secondary sliding surfaces with significantly greater burial depth. The dominant instability mode during this stage is characterized by collapse-sliding-tensile cracking-creep. Overall, the genesis mechanisms of slow-moving landslides induced during typhoon periods differ substantially from those of landslides triggered by ordinary rainfall events, and their deformation characteristics and instability mechanisms exhibit a strong positive correlation with rainfall intensity.
 

Slow-moving landslides; Genesis mechanism; Typhoon-induced rainfall; Deformation and failure modes