Study On Characteristics Of Soil Erosion Of Engineering Accumulation Under The Conditions Of Rainfall And Inflow

The engineering accumulation has become an important source of the soil erosion newly arising in production and construction projects.The erosion on the slope of the engineering accumulation was significantly influenced by the platform inflow.In view of the insufficient research on the soil erosion process of the engineering accumulation slope under the interaction of rainfall and inflow,based on the field investigation and the theory of soil erosion,two kinds of erosion driving forces were studied by the artificial simulated rainfall and inflow experiments.Among them,in order to quantify the contributions of the runoff and sediments,reveal the the critical flow on the master of erosion,and clarify the effect of rock fragment content on erosion and sediment yield under the interaction of rainfall and inflow of the engineering accumulation,the characteristics of soil water infiltration and sediment yield,the response of the hydrodynamic parameters of the slope on the erosion and sediment yield were analyzed.The results may have implications for understanding the hydrodynamic mechanism of soil erosion on the slope of engineering accumulation under different driving forces.The conclusions as follows:（1）The effect of the interaction of rainfall and inflow on the soil water infiltration of the engineering accumulation slope was explored.Under the experimental conditions,soil water infiltration rate of the slope surface decreased rapidly at first and then fluctuated with time.Compared with the single rainfall effect,soil water infiltration rate increased by 3.13%to 528.57%under the interaction of rainfall and inflow,while compared with the single inflow effect,the increase rate of soil water infiltration ranged from-34.62%to 273.08%.（2）The characteristics of runoff and sediment yield and erosion morphology were identified of engineering accumulation slope under the interaction of rainfall and inflow.Under the rainfall condition,the rates of runoff and sediment yield were distinct with different rainfall intensities over time,which showed that light rain intensity changed stably,while the heavy rain intensity fluctuated largely.In addition,there were obvious differences in the erosion morphology of slope under different rainfall intensities,with the light rain were scattered in small pits,while the heavy rain were strongly eroded and formed the discontinuous rills,and concentrated on the middle and lower parts of the slope.Furthermore,under the inflow condition,the rate of runoff fluctuated continuously over time,and the rate of sediment yield decreased over time.Meanwhile,there was no significant difference in the erosion morphology of slope with different inflow rate,which were all erosion ditches,and the developmental position was random.In contrast,under the interaction of rainfall and inflow,the rate of runoff fluctuated more violently and the amplitude of sediment yield fluctuated more dramatically over time with the increase of inflow intensity.The erosion morphologies of slope were all gullies,and when the rate of inflow was 20 L/min,the dominant erosion by inflow.When the rate of inflow was 25 L/min,the phenomenon of landslide occurred on the slope.（3）The contributions of the runoff and sediment on the slope of an engineering accumulation under the interaction rainfall and inflow were quantified.Under the interaction rainfall and inflow,the volume of runoff and sediment of the slope were all increased,and the increase of sediment volume was greater than that of runoff.Compared with the rainfall condition,there were significantly increased in the volume of runoff and sediment,with the increase of 86%to 629%and 86%to 4914%,respectively.Meanwhile,compared with the inflow condition,the volume of runoff and sediment also increased obviously,with the increase of 12%to 175%and 15%to 505%,respectively.There was an interaction between the intensity of inflow and rainfall,and both of them had significant effects on runoff and sediment under the combination rainfall and inflow on the slope of an engineering accumulation.（4）The response mechanism of runoff hydrodynamic parameters to erosion and sediment yield under the interaction rainfall and inflow was revealed.Under the experimental conditions,compared with rainfall,the flow velocity increased by 76.47%to185.71%under the interaction of rainfall and inflow,while compared with the inflow,the increase of flow velocity ranged from-21.95%to 28.57%.The slope water flow under rainfall condition was laminar and transitional,while under inflow condition,the slope water flow was turbulent and transitional.In contrast,the slope water flow under the interaction of rainfall and inflow conditions was turbulent and transitional,and the patterns of flow were supercritical flow and subcritical flow,the resistance coefficient increased over time under these three conditions.Furthermore,compared with rainfall,there were obviously increased in the water flow shear stress and the runoff power,with the increase of 145.68%to 1204.16%and 340.16%to 2415.15%,respectively under the interaction of rainfall and inflow.While compared with inflow,the water flow shear stress decreased by 3.76%to 70.86%and the runoff power decreased by 0.85%to 74.83%.（5）The effects of the interaction of rainfall and inflow on the parameters of soil erodibility and critical were clarified.Under the rainfall condition,the soil erodibility parameter in the model of water flow shear stress was 0.2×10^-3 s/m,and the critical flow shear stress was 2.0 Pa,while the rill erodibility parameter in the model of runoff power was 1.2×10^-3 s²/m²,and the critical runoff power was 0.25 N/（m·s）.In contrast,the soil erodibility parameter in the model of water flow shear stress was 2 times greater under the interaction of rainfall and inflow(0.4×10^-3 s/m)than that under the single rainfall condition and the critical water flow shear stress increased by 6 times.Meanwhile,the soil erodibility parameter in the model of runoff power was 1.2×10^-3 s²/m² and the critical runoff power increased by 18 times.（6）The effect of rock fragment content on slope erosion sediment yield and hydrodynamic characteristics of slope water flow were quantified.Compared with the pure soil,the rock fragment content of 20%and 40%could significantly reduce the runoff rate,soil erosion rate,and the velocity of overland flow,with the reduction of 60%to 82%,62%to 91%,and 43%to 55%,respectively.There was no obvious effect on the overland flow for the rock fragment content,but it would change the patterns of overland flow,such as transforming the transitional stream into a laminar flow.In addition,compared with the pure soil,the rock fragment content of 20%and 40%could significantly increase the roughness of slope,decrease the water flow shear stress and decrease the runoff power,with the response amplitude of 130%to 286%,52%to 89%,and 63%to 89%,respectively.