Analysis of landslide mechanism induced by excavation and rainfall: A case study of the Qianjin square landslide in Wanyuan City, Sichuan Province

In recent years, there has been a frequent occurrence of geological disasters caused by the coupling of human engineering activities and rainfall environment. However, research on the mechanism of coupling has not been deeply explored. In this paper, the landslide of Qianjin square in Wanyuan City induced by the coupling of excavation and rainfall is taken as an example, and the characteristics and formation mechanism of landslide deformation and failure are analyzed by combining the monitoring data of surface displacement and deep displacement of the landslide of Qianjin square and the rainfall data. The study shows that: (1) excavation is the main reason for the reactivation of the old landslide, while rainfall plays a triggering and accelerating role; (2) excavation provides good airspace conditions for the landslide on the one hand , and on the other hand causes the soil behind it to lose support, leading to the misalignment of the landslide from front to back; (3) after excavation, long-term strong to moderate rainfall in the study area, combined with tension cracks caused by excavation, make it easier for surface water to enter the interior of the slope. The bedrock fracture water is replenished by atmospheric rainfall, resulting in some unsaturated soil becoming saturated soil, increasing the pressure of pressurized water and decreasing effective stress. Additionally, groundwater may reach the slip zone and drive the deformation development. Finally, the process mechanism of landslide induced by excavation and rainfall coupling is proposed as “excavation-slope multi-stage cracking-concentrated rainfall-slip zone weakening-accelerated deformation”.