KINEMATIC CHARACTERISTICS AND NUMERICAL SIMULATION ANALYSIS OF "8·12" GIANT LANDSLIDE IN SHANYANG COUNTY, SHAANXI PROVINCE

On August 12, 2015, a giant landslide occurred in Yanjiagou Village, Zhongcun Town, Shanyang County, Shaanxi Province. The landslide debris destroyed and buried 18 houses, resulting in 7 people dead and 64 people missing. Based on extensive field geological investigation and UAV aerial survey, this paper provides a comprehensive description on the basic characteristics of the Shanyang landslide and makes engineering geological zoning. Then, the formation mechanism and movement process of the landslide are preliminarily revealed. Finally, the discrete element software PFC^3D is used to simulate the movement process of the Shanyang landslide, reproducing the whole process of starting, collision and accumulation along the apparent tendency direction under the action of gravity after the landslide body is destabilized. The main findings of this paper are as follows. (1)Shanyang landslide is a typical bedding rock slope with apparent tendency instability. The long-term bedding creep of the landslide mass, coupled with the surface water dissolution, eventually led to the shear failure of the locking section and the overall destabilization damage along the apparent tendency direction. (2)In the movement process of the landslide body, due to the obstruction of the front stable mountain, the movement direction of the Shanyang landslide was deflected twice by collision. Moreover, the special motion accumulation features, such as layer overlap, demolition movement and lateral squeeze slide, were produced. (3)Based on the accumulation characteristics and structural distribution characteristics of the Shanyang landslide, the movement and failure process of the Shanyang landslide are divided into seven stages, namely, the landslide creep and edge formation stage, the locking section shearing and slide initiation stage, the overall high-speed sliding stage, the collision and "emergency braking" stage, the detachment lateral extrusion sliding stage, the secondary collided and flowing stage and secondary collapse sliding of the scarp cliff. (4)The numerical simulation results show that the Shanyang landslide only takes 35 s from the initiation to the final stopping, with a maximum movement distance of 500 m and a maximum velocity of 36.2 m·s^-1.