Three-Dimensional Numerical Simulation Of Touzhai Large High-speed Long-runout Landslide-debris Flow

In 1991,high-speed long-runout landslide-debris flow occurred in Touzhai,Zhaotong,Yunnan.This article takes this event as the research object,the research method that combines field investigation laboratory and outdoor tests and numerical simulation.The 3D geological model of the Touzhaigou is based on real elevation data and selected the parallel bonding constitutive model as constitutive model.Inverted the whole process of starting,moving,accumulating,and stopping the movement of the high-speed long-runout landslide-debris flow.And adjust the parameters according to the actual accumulation and influence range of Tuzhaigou to get the morphological characteristics of the accumulation body under different bonding.Analyzed the numerical simulation results of Movement time,average movement speed,sliding body energy and morphological characteristics of accumulated body.The main conclusions are as follows:?1?Aiming at the problem of PFC3D's weak pre-treatment in establishing landslide model,based on the calculation model of Touzhai landslide-debris flow,a digital contour map was proposed based on Rhino5.0 to build a complex 3D geological model to make up for weakness in pre-processing of particle flow programs.According to the macro parameters obtained from the test,the simulated micro-mechanical parameters of the rock and soil are calibrated by a virtual uniaxial test.?2?The numerical simulation of the Touzhai landslide-debris flow has a movement time of about200 s,and reaches a peak speed of 82 m/s after 50 s.During the slide along the ditch all the way down,due to the winding and twisting of the ditch,the sliding body constantly collided with the mountain.At 65 s,80 s,and 95 s,the average speed decline rate increased significantly,and the particles climbed up.After the movement to 150 s,the average rate of decline slowed down significantly,so it can be inferred that the landslide-debris flow reached the ditch mouth.After the movement to 200 s,the average velocity of the landslide tended to 0 m/s.In a stoppage state.?3?By monitoring the speed and displacement of the"ball"units at different positions of the landslide body,it was found that the average speed of the spheres on the surface of the landslide body and the leading edge of the landslide body is greater,the farthest distance is,and it is at the leading edge of the accumulation fan.The spheres at the bottom and trailing edges are often more affected by the gravity and terrain of the upper sphere.Energy monitoring of the landslide shows that extremely large amounts of energy accumulate inside the Tuzhai high-speed remote landslide body reaching 1012 J.Within 1 minute of the start of the landslide movement,the particles were flying in a volley,and the percentage of adhesion failure increased with time,and the particles were highly fragmented.?4?Taking into account the debris flow loose medium cementation or overhead composition,the characteristics of the compressed air trapped in the continuous gradation of the debris causes the fluid to appear in the material.The characteristics of the long-distance movement in the Tuzhaigou with a low coefficient of friction are selected,and low friction is selected.The coefficient and the weak bond strength between particles are numerically simulated.By analyzing the stacking pattern of the Touzhai landslide-debris flow model,it can be inferred that during the landslide-debris flow movement,there are climbing phenomena on both sides of the mountain,Scraper effect.When the Tuzhai landslide-debris flow reached the mouth of the Tuzhaigou ditch,because it was no longer constrained by the mountains on both sides of the narrow gully,the detritus flow spread to both sides,eventually forming a"horn"-like morphological accumulation,and large-sized block stones.The findings of the survey agree.The particle flow discrete element program simulation PFC3D well inverted the whole process of the Tuzhaiyu speed remote landslide-debris flow from initiation to accumulation.By analyzing the simulation results,it is found that the PFC^3D particle flow program can better simulate the three-dimensional stacking morphology and influence range with reasonable parameters,and can provide a reference for delimiting the safe avoidance range.