Dynamic simulation insights into friction weakening effect on rapid long-runout landslides: A case study of the Yigong landslide in the Tibetan Plateau, China

This study proposed a novel friction law dependent on velocity, displacement and normal stress for kinematic analysis of runout process of rapid landslides. The well-known Yigong landslide occurring in the Tibetan Plateau of China was employed as the case, and the derived dynamic friction formula was included into the numerical simulation based on Particle Flow Code. Results showed that the friction decreased quickly from 0.64 (the peak) to 0.1 (the stead value) during the 5s-period after the sliding initiation, which explained the behavior of rapid movement of the landslide. The monitored balls set at different sections of the mass showed similar variation characteristics regarding the velocity, namely evident increase at the initial phase of the movement, followed by a fluctuation phase and then a stopping one. The peak velocity was more than 100 m/s and most particles had low velocities at 300s after the landslide initiation. The spreading distance of the landslide was calculated at the two-dimension (profile) and three-dimension scale, respectively. Compared with the simulation result without considering friction weakening effect, our results indicated a max distance of about 10 km from the initial unstable position, which fit better with the actual situation.