Movement Process Analysis of Long-Runout Guanling Landslide in Guizhou, China

On June 28, 2010, an extremely large landslide-clastic flow occurred in Dazhai Village (25°59′8.2″ N, 105°16′56.3″ E), Gangwu Town, Guanling County, Guizhou Province. The collapsed landslide had a volume of about 117.6 × 104 m3 and slipped 1.5 km along the direction of 325°, which destroyed 2 villages on the way and caused 99 casualties. Ultimately, the landslide-clastic flow accumulated on the valley with a volume of about 174.9 × 104 m3. In order to deeply understand the dynamic process of high-speed and long-distance landslide-clastic flow disaster, it is necessary to reveal the impact of the accumulation characteristics, velocity evolution process, energy transfer effect and motion trajectory characteristics of the collapsed landslide during the landslide movement process. The discrete element simulation software, Particle Flow Code in Three Dimensions, PFC3D, was used to simulate the entire process of Guanling landslide from initiation, high-speed descent to accumulation. Meanwhile, it is found that the residual friction coefficient of Guanling landslide was 0.29 and the damping was 0.05, the simulated accumulation characteristics were consistent with the actual situation. The results of simulation showed that the front-edge landslide started faster than the trailing edge, and there was a lag effect in time; the maximum speed was 33 m/s at the valley of Yongwo Village, the velocity of the left collapsed landslide decreased sharply after hitting Yongwo Village, and the velocity amplitude range was 4–10 m/s, showing a “single peak” characteristic. Due to good airborne conditions, the right collapsed landslide pushed and dragged the left blocks, forming a “second peak” in speed. The velocity amplitude range was 17–24 m/s, showing the characteristics of “double peaks”. Finally, it buried Dazhai Village and caused secondary loss in energy and velocity while it continued to move with a residual value (<2 m/s) until it reached zero at a standstill state. The accumulation of particles met the order law, and the overall accumulation distance was positively correlated with the division of block particles. According to the law of conservation of energy, the total energy consumed in the whole process was 4.65 × 1012 J and the conversion rates of peak kinetic energy, peak bond cracking energy, sliding energy and damping energy were 4.9%, 0.93%, 64.7% and 26.5% respectively.