Rainfall-induced landslides are a significant hazard in areas covered by granite residual soil in northern Guangdong Province. To study the response of granite residual soil landslides to rainfall, the most severely affected area during the floods in June 2022 and April 2024 was chosen as the study area. Geological investigations and field artificial rainfall tests were conducted to explore the deformation evolution characteristics of granite residual soil slopes under continuous heavy rainfall and to reveal the failure mechanism of rainfall-induced landsliding events. The results indicate that the granite residual soil can be divided into two layers, and the slope structure can be subdivided into three models from the geological point of view. Given that the deformation and failure characteristics of the surficial landslides are highly similar across the three models, the three models can be consolidated into a single model composed of granite residual soil and weathered granite. The intensity and persistence of rainfall are the main triggering factors of landslides in this area. The landslides are primarily characterized by surficial sliding with a traction sliding failure mode, mainly involving a granite residual soil layer thickness of about 1-3 m. The increased rate of water content and the range of pore water pressure can be used as primary indicators for slope deformation and failure. Additionally, shear dilatancy deformation during slope movement effectively mitigates deformation rates. Furthermore, debris flow is identified as a secondary disaster resulting from landslides, with landslide deposits serving as potential sources for debris flow.

The rapid movement and extensive displacement of gravel-silty clay landslides result in significant property damage and loss. Following the destabilization of the Shaziba landslide in Enshi City, it transformed into a debris flow, ultimately obstructing the Qingjiang River and creating a barrier dam. This study delves into the failure mechanism, leap dynamics, and motion processes of this specific landslide by employing a blend of ring shear testing and the discrete element method. Initially, the residual shear strength of the sliding soil was assessed through ring shear tests conducted under various coaxial stresses and shear rates within the sliding region, using field surveys and aerial imagery. Building upon this foundation, the entire progression of the landslide-from sliding to settlement-was replicated using PFC3D, allowing for an examination of the landslide's movement characteristics such as speed, displacement, and trajectory. The findings indicate that the shear displacement and residual friction coefficients are higher at elevated shear rates compared to lower rates. The landslide commences with an initial acceleration phase, with the silty clay material's movement lasting approximately 757 s, reaching a maximum velocity of 32.5 m/s and a displacement exceeding 1000 m. The simulated settlement volume of the landslide (9.31 x 105m3) closely aligns with the results obtained from field investigations (1.5 x 106m3). This research offers comprehensive insights into recent Shaziba landslides, serving as a valuable resource for enhancing our understanding of the dynamics involved and mitigating the potential risks associated with such events.