Experimental Study On Runoff Erosion Process And Influencing Factors Of Granite Residual Soil

Under the effect of water flow erosion,runoff erosion is very easy to occur in the collapse area,and runoff erosion gully is formed,resulting in serious soil and water loss.Granite residual soil is an important part of colluvial deposits in collapse area,which leads to the colluvial deposits has loose soil and poor structure.This paper explores the influence of slope(10°,20°,30°),the flow of runoff from upslope(450L/H,600L/H,750L/H),and initial water content(7%,11%,15%)on runoff erosion characteristics and failure patterns of slope gully depth and width.Through the dynamic analysis and systematic quantitative study of the hydraulic parameters of runoff erosion,the paper aims to explain the intrinsic mechanism of runoff erosion about gully slope sediment production and erosion evolution.(1)Based on the natural environment and soil condition of the granite residual soil in southern jiangxi province and literature references,the influencing factors of runoff erosion mechanism of the slope under the runoff from upslope condition are summarized that slope,the flow of runoff from upslope and initial water content are determined..(2)In this experiment,a model device is designed,which includes three systems:main water tank with variable slope,artificial effluent system and data collection system.The model can simulate the erosion process and morphological evolution of runoff erosion at different slopes and different runoff flows indoors.(3)According to the study of different factors,the hydraulic erosion process of runoff erosion on slope surface is as follows:flow sections-erosive pit-gully erosion,-slope bottom collapse-rill dehydration collapse.The higher the slope,the flow,and the the initial moisture content are,the more serious the erosion failure form is,lead to the larger the collapse range and the more the bottom tearing scouring phenomenon area.(4)Under each factor,the change rate and saturation degree of volume water content are mainly shown in the slope top>slope tail>slope middle.After reaching saturation,granite residual soil is more vulnerable to erosion.The saturated area increases with the increase of slope and flow,and decreases with the increase of initial water content.(5)Under the condition of large slope,large flow and high initial water content,the longitudinal development of gully depth and the transverse development of gully width were more intense.However,there is a common feature,that is the destruction of gully depth is the slope bottom>slope top>slope middle,and the destruction of gully width is the slope top>slope bottom>slope middle.(6)The sediment production in the early stage of runoff erosion is high,and the sediment production in the middle and late stage is reduced.The sediment production increases with the increase of slope,flow and initial moisture content,and the sediment yield is affected by channel development.Under the same conditions,due to infiltration effect,runoff is small of the runoff erosion in the early stage,the later development is stable.It is greatly affected by the flow that the large flow rate is more stable.The runoff increases with the increase of slope and flow,and decreases with the increase of moisture content.(7)Through the analysis of the hydraulic parameters of runoff erosion,the flow pattern in each experiment belongs to steep laminar flow.The increase of each factor will lead to the decrease of resistance coefficient and the increase of flow shear force and stream power,which will promote the erosion process of runoff comprehensively.For the change of initial water content,the erosion mechanism mainly comes from the stability of the soil,and the influence of hydraulic factors is small.