Study On Collapse Erosion Experiment And Numerical Simulation Of Water Migration Under Rainfall Conditions

The collapse of the small-scale existence in southern China is a serious form of soil erosion.This paper takes the granite residual soil of Yudu County,Ganzhou City,Jiangxi Province as the research object,through a rainfall device that can change the slope,to study the process of residual soil erosion and soil moisture migration under rainfall conditions;The process of the collapse of the slope at different slope angles.Model experiments based on the volumetric water content in the soil,pore water pressure,wetting front in the soil in the law of change in the law of the evolution of granite residual soil collapsing the intrinsic mechanism.This article also uses the Hydrus-3D numerical simulation software to further demonstrate the experimental results.The research results can be used as a reference for the prevention of the collapse.The main research results of this paper are as follows:(1)In the early stage of the rainfall model experiment,the author compared the average annual rainfall and temperature in Jiangxi Province and Yudu County by consulting the statistics bureau of Jiangxi Province and the national statistical yearbook.It was found that the annual average temperature in Yudu County was about 20 degrees Celsius.The annual average temperature is higher than the average temperature in Jiangxi Province.This kind of climate is suitable for the development of the collapse of the post,so Yudu County is the hardest-hit area in Jiangxi Province.Through statistics,it is found that the average annual collapse rate of Jiangxi Province in the past 15 years is about 27.3%,and the collapse has brought about non-negligible economic losses to the entire province.(2)According to experimental requirements,an experimental device and experimental method that can change the slope angle were designed and developed.Rainfall model experimental devices are mainly divided into a main model tank,a top rainfall device,a data acquisition device,and a rainwater collection device.(3)Through a single rainfall model experiment,it was found that the erosion rate at the bottom of the slope> the middle part of the slope> the top of the slope.Gullyerosion causes the soil mass to be suspended.Gravity causes vertical and horizontal cracks around the earth to cause the mass to collapse.The erosion process started from the bottom of the trench and the layers collapsed and developed towards the head of the trench.Comparing the collapse of the three experiments,the soil was not damaged after saturation.When the moisture content was 30% to 40%,it was the warning value of the collapse of the granite residual soil.(4)Through the experimental process of the model,it can be found that the erosion process of rainwater on the slope surface can be summarized as raindrop erosion ? erosion ? converging erosion ? trench erosion ? peeling and collapse.The slope failure mode is strip collapse,while the slope slope destruction mode is scoop failure.With the continuation of the rainfall time,the form of flat slope destruction developed towards the scoop collapse.The experimental collapsing form in this paper conforms to the classic collapse form system diagram.(5)The soil wetting peak of a gentle slope is generally divided into two stages,namely the fast-run period and the stable period.The wetting peaks of soils on steep slopes are generally divided into three stages,namely,rapid run,stagnation and stabilization.The period of rapid growth is between 1 hour and 1.5 hours.The slower the gradient,the better the water retention effect and the faster the water content of the soil increases,but the slower the collapse rate.(6)Hydrus-3D can simulate the process of water migration under the condition of rainfall.The simulation results are basically consistent with the experimental results.