Mechanisms of rainfall-induced landslides and interception dynamic response: A Case Study of the Ni changgou Landslide in Shimian, China

Geological hazards, especially landslides and mudslides, are frequent in Caoke County, Sichuan Province, China. In September 2022, a large-scale mudslide occurred in Ni changgou with continuous rainfall, and it caused great damage to the surrounding roads and downstream village buildings. The mechanical parameters of the soil were obtained through a basic investigation of the landslide characteristics of Nichanggou. Upon that, the finite element-discrete element method was used to reconstruct the three-dimensional numerical model of the landslide on the right bank of Nichanggou, and the initiation mechanism of rainfall on landslide and the formation of debris flow impact dam process were simulated. Furthermore, the pore pressure, stability coefficient as well as displacement of the landslide body were analyzed, it turned out that under long-term continuous rainfall conditions, the slope safety factor decreases with the increase of rainfall time by analyzing the pore pressure, stability coefficient and displacement of the landslide body, which exist under different conditions of heavy and extreme rainstorms. Then the laws affecting landslide initiation and damage characteristics could be found out. The duration of landslide movement is about 200 s, the maximum average velocity of the landslide reaches 4.85 m/s, and the average movement distance is close to 500 m. These measured data matches well with that simulated landslide mound morphology.In addition, as the downstream debris flow washout is part of the initiating material source, the topography and debris flow are simplified accordingly, the whole process of impact, climbing height and back silting of the debris flow impact blocking structure is reproduced. The coupled method shows the whole process of debris flow from formation, to blocking, The results show desired effect on the mudflow prevention and management.