Effect Of Soil Bulk Density On Soil Erodibility

This paper mainly analyze the change characteristics of runoff and sediment yield on the slope surface,and the variation law of various hydrodynamic parameters by using simulated rainfall experiment under different rainfall test conditions.The relationship between average sediment yield rate of slope erosion and hydrodynamic parameters was established.At the same time,the physical and chemical properties of soil and the K value of soil erodibility were used to modify nomo formula,then a modified model of K value of soil erodibility including soil bulk density was established.The main conclusions are as follows:(1)When the rainfall intensity is the same,the runoff time on slope generally shows a law of gradual decrease with the increase of soil bulk density.When the soil bulk density is the same,the runoff time on slope gradually advances with the increase of rainfall intensity.When the rainfall intensity is relatively small,the change of soil bulk density has a certain influence on the runoff time on the slope,but when the rainfall intensity increases to 60mm/h,the influence of the change of soil bulk density on the runoff time on the slope is masked by rainfall intensity to some extent.(2)The average runoff yield rate of slope increases rapidly at the initial stage of runoff yield,and then stays at a high value and stable state with the extension of runoff yield duration.However,the average sediment yield on the slope increases rapidly at the initial stage of runoff yield,then declines after reaching the peak,and finally reaches a stable state.When the soil bulk density is consistent,the average runoff yield and average sediment yield increase with the increase of rainfall intensity.When the rainfall intensity is consistent,the average sediment yield and average runoff yield increase with the increase of soil bulk density.(3)When the rainfall intensity is the same,the accumulated runoff,accumulated sediment,average flow velocity,runoff depth,Reynolds coefficient,Froude number,unit flow power,flow shear stress and flow power all increase with the increase of bulk density.When the soil bulk density is the same,the accumulated runoff,accumulated sediment,average flow velocity,runoff depth,Reynolds coefficient,Froude number,unit flow power,flow shear force and flow power all increase with the increase of rainfall intensity.There is a very significant linear relationship between soil bulk density and accumulated sediment,and the determination coefficient R~2 is greater than 0.97.(4)Under the condition of simulated rainfall test,Re is less than 500 and Fr is greater than 1.According to the evaluation criteria of open channel flow regime,the runoff flow regime under different combination conditions of soil bulk density and rainfall intensity belongs to laminar torrent flow.However,from the overall analysis of the experimental data,the flow regime on the slope is not entirely laminar,but a“disturbed flow”.(5)Under the condition of simulated rainfall test,there is a power function relationship between the average sediment yield rate on slope and each hydrodynamic parameter,and the determination coefficient is greater than 0.8.Among them,the determination coefficient between flow power and average sediment yield rate on slope is the largest(0.9750),which indicates that flow power can better predict the sediment yield rate of slope erosion,thus indicates that water flow energy parameters can better reflect the process of soil erosion than the force acting on soil.(6)Under the condition of simulated rainfall test,there is a positive correlation between soil erodibility K value and soil bulk density.The K value of soil erodibility obtained from rainfall experiment was used to modify nomo formula,and the K value modified model of soil erodibility including soil bulk density was established.The determination coefficient of the model is 0.7189,which indicates that the modified model has a certain accuracy and can be used to correct the K value of soil erodibility.