Investigation and numerical modeling of the overloading-induced catastrophic rockslide avalanche in Baige, Tibet, China

After the first high-position landslide occurred in Baige Village, a second slide originated from the crown of the first landslide on November 3. The approximately 1.6 million m³ second slide moved rapidly and applied an impact load on the upper part of the residual mass of the first landslide, resulting in a 6.6 million m³ entrainment volume. The sliding mass rushed into the Jinsha River and blocked the channel again, causing catastrophic flooding which destroyed numerous roadbeds, bridges, and a large number of residential houses in Sichuan and Yunnan provinces. Based on field investigations and simulation results by dynamic discrete element method (DEM), after the first landslide, the blocks formed by the trailing edge of the landslide became unstable and slid, continuously and dynamically loading and accumulating on the upper part of the first debris deposit, which rested in the grooved terrain of the slope, leading to the instability of the residual slope’s rock–soil mass and the initiation of a debris avalanche. With a peak velocity of 62 m/s, the debris avalanche slid rapidly to the location of the first slide deposit. Due to the topographic effect, it was transformed into a diffused debris avalanche, which scattered and accumulated, exhibiting the typical characteristics of a rapid long-runout landslide. Then, the calculated velocity value by DEM was also compared with those using other dynamic modeling approaches (e.g., sled model and rheological model). The DEM was proven producing a reasonable velocity variation pattern, and thus, it is suitable for the simulation of the entire movement process of high-position rockslides similar to the second Baige landslide.