Study On Drag Effect Of Flow Like Landslides

Flow-like landslide is one of the most common geological disasters in western mountainous areas of China.It has the characteristics of fast movement,large impact energy,and wide disaster range.It usually forms a chain of "slides-debris avalanche-debris flow".In the process of movement,the collapsing body undergoes the movement of solid blocks and disintegrates into debris flow movement,and then further transforms into multiphase fluid movement due to the influx of rainwater,ice and snow melt water and other fluids.Multiphase fluids have complex interactions between fluids and solids when they are in motion,which further enlarges the scale of disasters and brings great damage to human life safety and engineering construction.This paper studies the drag effect of two-phase fluids through geological model establishment,dynamic mechanism analysis,numerical simulation calculation and example verification,and draws the following conclusions:(1)Through previous data analysis and field investigation,the basic characteristics of typical fluidized landslides in western mountainous areas of my country were summarized,and the movement geological model of "high-level initiation-collision disintegration-fluidized accumulation" was established,revealing high-level remote fluidized landslides The movement and accumulation process from rocky solid block to detrital particle flow to multiphase fluid.At the same time,it is believed that the interphase force between liquid and particle plays a key role.(2)Using related basic theories such as particle mechanics,contact mechanics and computational fluid dynamics,derives the particle dynamics model and fluid balance equation in fluidized landslides.And use Wen&Yu model and Ergun model to establish the mechanical relationship between particles and fluid.(3)The solid-liquid two-phase drag force of a fluidized landslide has an important effect on the disaster range of the landslide.The difference in solid-liquid velocity,liquid properties and liquid volume ratio affect the movement characteristics of solid particles.Through comparative analysis,it is found that different liquid properties have different drag effects on solid particles;when the difference in velocity between liquid and solid is greater and the proportion of liquid volume is higher,the longer the solid movement distance and the faster the movement speed.(4)The dynamic analysis method of fluidized landslide based on VOF-DEM was used to reproduce the whole process of dynamic disaster of landslide and debris flow of Xianchi Reservoir in Yunyang County,Chongqing.According to the simulation results,the movement speed and accumulation distance of fluidized landslides are mainly affected by two factors: one is the blockage of terrain such as valleys,and the other is the dynamic action of liquids such as mud or water accumulated on the surface during rainfall.The dynamic action of liquid on solid particles is embodied in energy transfer effect and drag reduction effect.(5)Through comparison,it is found that the movement distance of the debris flow of the same volume is much smaller than that of the debris flow,but the instantaneous kinetic energy of the debris flow is greater than that of the debris flow when a disaster occurs.Therefore,the disaster-causing scope of debris flow is wider and the movement lasts longer,which provides a certain theoretical basis for the prediction and prevention of the disaster-causing scope of debris flow in western mountainous areas of my country.