Deformation response and mechanism induced by rainfall of the Zhoujia landslide in Southwestern China

Due to complex engineering geological and hydrological conditions and proximity to the dam site, the Zhoujia landslide has a potential instability risk, which poses a significant threat to the safety of the downstream hydropower station. In this study, a comprehensive assessment of the deformation characteristics and failure mechanisms of the landslide is conducted through field investigations, in situ monitoring data, and numerical simulations. The results indicate that the Zhoujia landslide is a giant ancient accumulation-landslide currently in the creep deformation stage. The deformations are mainly concentrated in Zone B1, which shows a tendency of frontal traction and rearward tearing and no sign of convergence yet. Meanwhile, Zones A and B2 show smaller and converging deformations. The correlation analysis reveals that rainfall is the primary triggering factor for landslide deformations, with a time delay of 1–2 months. Preliminary judgment based on numerical simulation of the landslide’s plastic zone indicates the Zhoujia landslide exhibits typical layered failure characteristics. Three potential failure patterns of Zone B1 are identified: sliding along the shallow gravel silt layer, sliding along the deep gravel silt layer, and overall sliding along the bottom sliding zone. The study’s findings will provide guidelines for early warning and engineering control of the Zhoujia landslide during the construction and after the completion of the Kala Hydropower Project.