Study On Impact Characteristics Of Collapse Debris Flow

The collapse debris flow in mountainous areas has the characteristics of high position,long-distance and high speed,which poses a great threat to the lifeline engineering and people's property safety in mountainous areas.Therefore,the study of its impact characteristics will play a guiding role in the design and prevention of damage to mountain engineering structures.In this paper,the matrix discrete element program MatDEM is used to analyze the motion process of the collapse debris flow,the dynamic impact,the accumulation characteristics after the end of the impact,and the influence of debris factors and slope factors on the impact force of the dry debris flow.Mainly achieved the following conclusions:(1)The dry debris flow moves on the slope,and the range of motion is a fan-shaped area.The movement mechanism has both friction mechanism and collision motion mechanism.The velocity distribution during the movement of dry debris flow particles shows that the leading edge velocity is much longer than the trailing edge velocity,the upper velocity is greater than the lower velocity,and the intermediate velocity is greater than the edge velocity.The process of clastic flow impacting the structure is a continuous impact for a certain period of time.It is divided into the power impact phase and the final stationary phase.The impact force first increases to a certain peak value,then decreases,and finally reaches a stable residual accumulation force.(2)During the movement of the collapse debris flow,the initial gravitational potential energy is gradually transformed into kinetic energy,and part of the thermal energy is generated due to the frictional collision between the particles and the particles and between the particles and the slope,which is dissipated as heat.When the dry debris flow begins to impact the structure of the bottom of the slope,the kinetic energy is gradually transformed into impact energy.After the formation of the accumulation body in front of the structure at the end of the impact.At this time,the impact can reach the maximum.(3)From the particle velocity distribution vector diagram during the movement of the collapse debris flow,it can be seen that the dry debris flow has the action of the cutting blade.The velocity vector direction of the bottom part of the dry debris flow intersects with the surface,indicating that the bottom particle collides with the surface,the leading edge particle exhibits a shovel action,and the middle trailing edge particle exhibits a scraping effect.(4)The longitudinal flow of the dry debris flow accumulation body is a trapezoid with a free surface and a straight line.As the slope of the sliding bed increases,the height of the dry debris flow accumulation in front of the structure is higher.The dry debris flow accumulation force of the structure decreases with the increase of the height of the structure,and the total accumulation force increases with the increase of the slope of the sliding bed;The dry debris flow deposits appear to have the largest intermediate stack thickness in the lateral direction,decreasing sequentially toward both sides.When the creeping surface is a curved surface(cylinder pier),the accumulation thickness of the deposit is smaller than that of the flat surface(cubic house),and the distribution of the dry debris flow accumulation of the structure in the lateral direction is consistent with the quadratic parabolic distribution pattern.The main performance is that the central part of the impact surface has the largest stacking force,and decreases to the both sides.Under the same size condition,the total stacking force before the curved surface structure is smaller than the front surface of the flat surface structure.(5)Characteristic impact force(maximum dynamic impact force,residual accumulation force)of The collapse dry debris flow have a certain relationship with clastic flow volume,clastic flow particle size,internal friction coefficient of clastic flow,buffer length and Sliding bed roughness and slope of the sliding bed.The influence of clastic parameters is as follows: the maximum dynamic impact force of collapse dry debris flow increases with the increase of dry debris flow volume and dry debris flow particle size,decreases with the increase of internal friction coefficient of dry debris flow particles.After the end of the collapse dry debris flow,the residual accumulation force increases with the increase of the dry debris flow volume and the dry debris flow particle size,decreases with the increase of the internal friction coefficient of the dry debris flow;The influence of slope parameters is as follows: the maximum dynamic impact force of the collapse dry debris flow increases with the increase of the slope,decreases with the increase of the buffer length and the roughness of the slope.After the end of the collapse dry debris flow,the residual accumulation The force increases with the increase of the slope,decreases with the increase of the buffer length and the roughness of the slope.