Research On The Starting Conditions And Flow Characteristics Of Debris Flow

In recent years,debris flow disasters often occur,especially large-scale debris flow disasters have caused serious harm to people's life safety and large-scale lifeline projects.The starting condition of debris flow is of great significance to the prediction and evaluation of debris flow,but the starting condition of debris flow is not mature compared with the study of dynamic process of debris flow.Since large debris flow disasters are also often classified as debris flow in recent years,the debris flow concerned in this paper is in a broad sense,including traditional debris flow and debris flow.The start-up of debris flow is the unstable process of particle accumulation under the action of flow and other external forces.This paper studies the start-up problem of debris flow through indoor experiments and certain theoretical analysis.In this paper,a rotary chute test system is designed and built,which includes control system,measuring system,water flow system and other subsystems,which is used to study the starting conditions of debris flow.The research content is divided into two parts:slant groove debris flow test research,debris flow under the action of water flow start test research.The main tasks of slant-slot debris flow test research are as follows:1).the start-up mode of debris flow under the condition of no water concideration;2)characterization of the characteristics of debris flow movement under waterless condition;3)analyzing the stress relationship of surface particle of accumulation body and obtaining the expression of debris flow starting condition.The research tasks of the debris flow start-up test under the action of water flow are as follows:1)observing the characteristics of particle accumulation motion under the action of water flow;2)characterizing the seepage characteristics inside the inclined groove accumulation body;3)quantifying the influence of water flow on the accumulation body flow and obtaining the expression of debris flow start-up condition under the seepage condition.By analyzing the experimental data,the following conclusions are obtained:1?It is found that the accumulation structure,particle size and particle matching ratio have great influence on the start of debris flow:1)The smaller the particle size in the chute,the greater the rest angle,and the more times the stack starts;2)the collapse characteristics of heterogeneous particles,affected by the interaction between the constituent particles.2?The mechanical analysis shows that the number of collapses depends on two key physical parameters:wall friction angle,starting friction angle and repose angle.In this paper,the expression of the starting condition of debris flow under anhydrous condition is obtained by data fitting.3?There are three stages in the initiation of debris flow under the action of water flow:seepage stage,runoff scour stage,runoff erosion stage.There are two kinds of motion forms of particles in the seepage stage:continuous loss of particles and falling of particles collapse.4?The starting mechanism of debris flow under seepage action is as follows:the lubrication effect of pore water on the accumulation body when the slope angle is small makes the structure unstable,and the seepage pressure destroys the accumulation structure when the slope angle is large.In this paper,the expression of debris flow starting condition is obtained by data fitting.