Research On Dynamic Characteristic And Simulation Of Debris Flow

Debris flow refers to the loose rock and soil sliding along the slope under the action of weathering and earthquake and blasting and may be further broken in the motion process.It is a special and common geological disaster phenomenon.Debris flow often has the characteristics of high speed,long distance and strong impact.The main difference with the common debris flow for the motion is mainly influenced by the collision and friction of rock and soil.It will bring great damage to human life and economy.In this paper,the characteristics and mechanism of debris flow dynamic process have been researched in order to improve the understanding of debris flow disaster,which will provide scientific basis and reference for disaster prevention and reduction.In recent years,many scholars have made some progress in the research of debris flow disasters.However,because of the complexity of the process,it is necessary to carry out a more in-depth research.Firstly,according to the continuum theory,a depth averaged model is developed to describe the dynamic process of debris flow.The finite volume numerical method has been used to solve the model,and the HLLC approximate Riemann solver has been used to calculate the interface flux of the control unit.At the same time,the theory of discrete element model and its solution method are introduced.So as to lay a foundation for the comparative research of the applicability of debris flow simulation methods.Secondly,the experimental and the simulation research of the particle material collapse characteristic have been carried out.Based on the whole collapse experiment,the partial collapse experiment has been carried out,and the variation rule of the final accumulation parameters of the granular material has been obtained.Based on the analytical verification of the depth averaged continuum theory method,two kinds of calculation methods including continuum theory method and discrete theory method have been used to simulate the collapse of granular materials.The results show that the discrete theory method is in good agreement with the experimental results as the existence of the static core and the vertical acceleration,which verify the effectiveness of the discrete theory method.And the characteristics of particle collapse process are analyzed and discussed based on the simulation.Thirdly,combined with the experiment of debris flow sliding along the chute,the numerical simulation of the clump model is carried out.The correctness and effectiveness of the clump model are verified by comparing the simulation results and the experimental results.At the same time,the normal force of the wall is calculated by using the depth averaged continuum theory method.The results show that the two methods are in good agreement with the experimental results.However,the discrete theory method can capture the peak value of the impact force which is more important to the protection structure,and the depth averaged method can not capture the peak value of the impact force due to the assumed conditions.And,the motion characteristics of debris flow velocity profile and the dynamic characteristics of particle size separation are analyzed and discussed based on the simulation.Fourthly,in order to simulate the erosion process in the motion process of debris flow,the experimental flume has been designed.The effects of the source material quality,the source height and the length of the erosion area on the erosion process and the mechanism of the erosion process have been researched.The results show that the apparent erosion occurs only when the amount of erosion is greater than that of the deposit.The material in the source area is eroded by the impact of the scraper and the impacting.The wake also produces deposits in the erosion zone.Erosion is positively correlated with the quality and relative height of the source area,but negatively correlated with the length of the erosion zone.The numerical simulations were carried out using depth averaged continuum theory method and discrete theory method.The results show that the continuum theory method is not suitable for the local limited erosion area,and the discrete theory method is more suitable.And,the accumulation form,particle velocity vector and erosion process are analyzed and discussed based on the simulation.Finally,two typical debris flow disasters were taken as the case,and the numerical simulations of debris flow disaster process were carried out by using two kinds of simulation methods.According to the characteristics of the engineering case,the process of velocity and energy and the influence of local topography on the disaster process have been discussed.The results of two kinds of simulation methods are in good agreement with the actual disasters.The simulation results show that the two kinds of methods are applicable to large scale disaster calculation.In the aspect of computational efficiency,the continuum theory method is better.