Investigation and characteristic analysis of a high-position rockslide avalanche in Fangshan District, Beijing, China

At 8:30 a.m., on August 11, 2018, a high-position rockslide avalanche was reported in Da’anshan village, Fangshan district, Beijing, China. The landslide destroyed the road below and did not cause any casualties due to the timely detection of warning signs. The displaced landslide material traveled a horizontal distance of about 260 m with a vertical drop of about 176 m and stopped at 613.6 m asl. According to videos and survey data, the Da’anshan rockslide initiated at a high position and transformed into a pipeline-type debris avalanche along the gully to the east. It scraped the surface layer of the strongly weathered rock formation and also transformed into a diffuse-type debris flow along the slope surface. Finally, it accumulated at the bottom of the river valley and presented a typical disaster mode of rapid runout. Based on this, the Archard erosion model was embedded in the Engineering Discrete Element Method (EDEM) to perform back analysis and simulate the three-stage kinematic processes of sliding, shear-shoveling, and flow accumulation to quantify the scraping volume and position. After initiation at a high-level position, the rockslide moved downward along the valley for approximately 10 s with a maximum velocity of 26.1 m/s. The final volume of the accumulation obtained from the simulation was ~24,000 m3, which is close to the total volume obtained from the field investigations. This study provides a methodological reference for future simulation analysis of high-position rockslide avalanches.