Research On Debris Flow Disaster Numerical Simulation And Its Prevention And Control

Debris flow is a kind of frequent geological disasters which is often happen in the mountainous area,do great harm to people's life and property safety.Research on debris flow disaster mechanism and mitigation have been two important research subjects.In recent years,discrete element method has been more and more widely used in the field of geotechnical engineering,especially in numerical simulation of debris flow evolution.The main advantage is that it can attain more accurate results than continuum or finite element method in solving the questions such as large deformation of debris flow and considering the interaction among particles-fluid.The paper reviewed the present situation of domestic and foreign research,and combined theoretical analysis and numerical simulation.The main contents are as follows:(1)Theoretical model of debris flow evolution.In order to explain the kinetic mechanism of debris flow,based on Bingham fluid model and some assumptions,this paper established constitutive model to calculate the velocity and shear force of debris flow,as well as the improved formula of Bingham fluid model.This paper set up the constitutive model of startup of rainfall induced debris flow and particle separation.This paper deduced the control model of velocity and shear force,as well as the improved formula of Bingham fluid model by considering the coupling effect of new-type dam and debris flow.(2)Numerical simulation analysis.With the help of mapping software Pro/E and CATIA,this paper established a three-dimensional model of Dadi valley on the use of Dadi valley three-dimensional contour map and simulated the evolution of debris flow disaster by EDEM software.This paper analyzed the influence of the degree of curvature of the gully and the loose material on the surface and rainfall on debris flow.This paper explored the impact of particle morphology and particle interactions on the movement of debris flow.Effects of rainfall on debris flow were expressed in that it could weaken the soil shear strength and caused soil instability.The greater the rainfall intensity,the greater the startup velocity and runoff velocity.The change of frictional resistance of channel surface which was caused by loose material was the main reason for debris flow forming a leading effect.S-shape and S*-shape channels would change the way of debris flow and weaken its energy.The greater the channel bending,the greater the velocity decreases.Under the same condition of the source volume and other parameters,size of basic unit had an influence on the dynamic characteristics of debris flow,but it was not obvious.For the whole,the smaller the basic unit,the faster the velocity at early stage,the slower the late deceleration.For a single particle unit,the smaller the particle size,the greater the maximum displacement,the smaller the energy loss.(3)Disaster prevention and control engineering.This paper calculated the related parameters based on field exploration data and designed three kinds of dam engineering:gravity dam combination,a new-type dam and hybrid dam combination.This paper added each dam engineering to the three-dimensional model of valley to simulate the effect of dam on debris flow by using EDEM software.Basing on the numerical simulation results,this paper compared the effect of three kinds of dam engineering on disaster reduction and put forward protection suggestions based on the conclusions.The results showed that dam could change the motion path of debris flow.Gravity dam combination acted as a buffer,intercepting debris flow twice,reducing the velocity and weakening the impact force,to prevent most of debris flow to arrive downstream area.A new-type dam mainly acted as a guide and took debris flow to designated areas.With a safe height,a new-type dam could help to form safety areas in the downstream.Hybrid dam combination had comprehensive effects on debris flow,intercepting debris flow and changing the way.In that condition,debris flow was more likely to turned to the designated area because of the low energy after being intercepted by a gravity dam.Accordingly,the destructive force acting on the new-type dam in the deceleration zone was so weak that could prolong its life cycle.Different combination of dams led to different cost and function,therefore,the most suitable combination should be chosen to reduce disaster according to the actual situation in the area.As above,conclusions in this paper will provide the effective reference for the evolution theory,numerical simulation and disaster prevention and control research of debris flow disaster.The conclusions also have good theoretical significance and practical application value.