Dynamics process simulation of long run-out catastrophic landfill flowslide on December 20 th，2015 in Shenzhen, China

In this paper, DAN3D numerical method is used to simulate the Shenzhen landfill landslide, and the dynamic disaster process is discussed. The conclusions are as follows: (1) the post failure movement of landslide was mainly divided into two stages: the previous stage was in the source area, which reflected the main body dynamic shear of high pore water pressure, and the latter stage is in the propagation area and accumulation area, which reflects the flow (surging) shear of the highly saturated sliding body. (2) In the analysis of the hydrodynamic movement of saturated soil landslide, the friction model is suitable for simulating the unstable sliding shear process under pore water pressure, and the Bingham model is suitable for simulating the fluidized shear process. The Friction-Bingham (FB) combined model is more suitable for the inversion or prediction of the whole process of the landslide. (3) the velocity change of the failure motion after the landslide in Shenzhen mainly goes through the process of starting-accelerating-holding-decelerating. The solid-flow conversion causes the huge casualty loss, in which the water is the key factor which the Shenzhen landslide dynamics causes the disaster. (4) The simulation result shows, the average stacking thickness is 11 m, the accumulation range is 0.4 km 2, the maximum velocity is 30 m/s, and the maximum velocity occurs at 620 m from the back edge of the landslide. The accumulation range, thickness and velocity are basically consistent with the actual value of the landslide. The above research ideas and methods can be used for reference in the hazard zoning of residual landslide in urban geology and the scientific site selection assessment of residual soil site.