Study On The Initiation Mechanism And Kinematic Mechanism Of Collapsed Clastic Grain Flow

The clastic grain flow is a kind of geological phenomenon in which the high collapsed body collides with the surrounding rock and soil body during the movement and the debris is continuously degenerated to produce fluidized motion.This paper focuses on the clastic grain flow disasters in southwestern China in recent years.On the basis of collecting and collecting the typical clastic grain flow case data,the movement process of the collapse-clastic grain flow disaster is summarized,and the starting mechanism and movement mechanism of the clastic grain flow are studied by theoretical analysis and numerical simulation.The main conclusions are as follows:(1)From the perspective of topography,landslide hazard zoning and clastic grain flow movement process,the investigation data of the clastic grain flow disaster in Mianyang Wenjiagou,the Daguangbao clastic grain flow disaster in Anxian County and the Yigong clastic grain flow disaster in Tibet are analyzed.It is found that the clastic grain flow in the western alpine valley region is mainly the collision clastic grain flow,and the overall movement process of the collapse-clastic grain flow can be divided into the collapse movement stage,the clastic grain flow acceleration stage and the clastic grain flow accumulation stage.(2)This paper divides the area of the disaster area affected by the clastic grain flow in southwest China,and counts the slope changes of each section.Combined with the research results of the existing clastic grain flow motion process,the short-range motion model of the collapse body including the rapid start acceleration process,the short-range travel acceleration process and the volley motion process and clastic grain flow motion slope model consisting of three-stage slope is proposed.(3)According to the movement process of the collapse body,the clastic grain flow fracture formation mode is divided into four categories,namely,short-range acceleration-volley leap collision fracture,short-range acceleration impact fracture,collapse impact fracture and sliding disintegration.Using the principle of pulverization mechanics,the critical speed of the collapse body is determined to determine the speed condition of the collapse of the collapse body to form the clastic grain flow.(4)The process of particle velocity changes in the same layer inside the clastic grain flow is basically the same.According to the changes of the moving speed of the bottom layer,the middle layer and the surface,the whole is the closer to the upper surface,and the faster the particle movement speed.From the stacking result,the internal particles move from the surface layer to the bottom layer.The larger the particle size of the crumb,the farther the migration distance is;as the height increases,the influence range of the debris body becomes larger;the slope accumulation section plays a buffering role and contributes to the remote migration of the clastic grain flow.(5)The final clastic grain flow of the simulated clastic grain flow has the characteristics that the front part is scattered and the height of the stack from the trailing edge to the leading edge is decreasing.As the initial height of the deposit increases,the overall horizontal displacement of the particles increases,and the relative distance between the surface particles and the underlying particles also increases significantly.Eventually,the particle packing is more scattered,and the influence range of the clastic grain flow is increased.(6)The internal motion form of the debris particles is mainly bouncing and rolling.The particles near the center of the initial slider have more movement deflection and larger deflection displacement.The closer the initial position is to the back of the sliding source area,the more the number of bounces in subsequent movements,but the bounce height is generally small;the closer the initial position of the particles is to the surface of the debris accumulation,the more the number of bounces in subsequent movements.