Effects Of Water Flow Strength Parameters And Root Density On The Detachment Capacity Of Undisturbed Clay Loess Soil

Soil detachment is the initial stage of slope water erosion and the main link of the source of slope sediment,which is one of the most basic and important stages in soil erosion research.The study of soil detachment capacity can fundamentally control the sediment production and the development of subsequent stages.The erosion process occurs at the interface of the two phases.Therefore,the size of the soil detachment capacity is the result of the interaction between the erosion ability of the water flow and the erosion resistance ability of the soil..In this paper,the evolution law of hydraulic characteristic parameters and its influence on soil detachment capacity were studied by constant bed resistance scour test,and the effect of root density on soil erosion resistance was pointed out by comparing root soil with bare soil.The following conclusions were drawn:(1)The response of soil detachment capacity to unit discharge was more intense according to the dual power function equation and two-factor ANOVA.Among them,the F statistics of unit discharge and slope were 53.086,32.785,and the power exponent of unit discharge and slope was 0.745,0.568,respectively.The power exponent of flow rate was31.16%larger than that of slope.There was a significant positive correlation between soil detachment capacity and water flow shear stress,which could be well described by linear equation.The slope of linear equation,that is,the shear stress erodibility coefficient of Yangling clay loess soil was 0.011 s/m;and the variation trend of soil detachment capacity with mean velocity and unit energy of section was also linear positive correlation;compared with the other parameters,the fitting effect of unit water flow power was relatively poor,and the correlation coefficient was 0.763;in this test,the water flow power was the most closely related to the soil detachment process,and the water flow power erodibility coefficient was0.01 s~2/m~2.(2)The response of flow power to unit discharge was the most intense,followed by unit energy of section,unit flow power and shear stress.The shear stress index and flow power index increased with the increase of unit discharge,and there was no tendency to slow down in the test range,while the unit energy of section and unit flow power of section were gradually stable with the increase of unit discharge.The unit flow power was most sensitive to the change of slope factor,followed by flow power,shear stress and unit energy of section.The flow power and unit flow power increased continuously with the increase of slope,while the shear stress index and unit energy of section index had a stable trend.Compared with slope and flow rate,the response of water flow intensity indexes to roughness or submergence degree was weak,in which the unit flow power and unit energy of section decreased with the increase of submergence degree;while the shear stress index was positively correlated with submergence degree;the response of water flow power index to submergence degree was the weakest,and the trend decreased slightly.The mean velocity was more sensitive to the change of flow rate,while the surface velocity was more sensitive to the change of slope.According to the fitting equation,the mean velocity and the surface velocity decreased with submergence degree in the form of power function.When the submergence degree was about more than 0.4,the decreasing trend of the mean velocity and the surface velocity tended to be flat.(3)Soil detachment capacity and relative soil detachment capacity decreased exponentially with the increase of root length density,root weight density and root surface area density,and the correlation between them and root surface area density was the highest.There were two critical values for root surface area density.When the root surface area density was less than 0.2 cm~2/cm~3,the erosion resistance of root soil complex was sensitive to the change of root morphological characteristics,and when the root surface area density was higher than 0.4 cm~2/cm~3,the increase rate of root soil complex was obviously weakened.In this paper,the soil erosion resistance coefficient from the mechanical point of view of soil erosion was used as the quantitative index of soil erosion resistance.The results of this study showed that mean erosion resistance of bare soil was 14.41 J/(m~2g),while that of root soil was 38.48 J/(m~2g),which was 2.67 times that of bare soil.