Study In The Process Of Rill Erosion Of Sediment Transport Capacity And Detachment Capacity Of Rill Flow Of Loess Soil

Due to the complex geographical features of the loess plateau,uneven topography and loose soil structure,the vegetation in the area is sparse,desertification is serious,in addition to the unstable climatic factors in the area,rainfall distribution is uneven,the annual variation is very large,which makes the ecological environment extremely fragile,and rill erosion is more and more serious under all kinds of factors on the loess plateau.Frequent rill erosion has resulted in the loss of nutrients from the soil plough layer,resulting in severe soil degradation and limiting the sustainable development of agriculture in the loess plateau,in addition,serious soil and water loss will lead to frequent natural disasters,to the local life and property security pose a serious threat.Therefore,the study of rill erosion process on the loess slope and the prediction of the amount of eroded soil are of great significance for the sustainable development of the loess plateau.In order to explore the rill erosion characteristics and the regularity of runoff and sediment production in the soil of the loess plateau under the erosion of runoff,we takes the loess soil on the loess plateau as the research object and set 4 slopes（5°,10°,15°,20°）and 3 flow rates（2 L/min,4 L/min,8 L/min）,then we carry out an indoor scouring test on the soil by using a limited rill with a width of 10 cm,which made us get the sediment transport capacity and the denudation capacity of the slope flow,combined with the runoff sediment concentration and the runoff shear force generated during the scouring process,the attenuation coefficient of sediment concentration as a function of rill length and the soil erodibility parameters were obtained.The main results as follows:（1）The sediment transport capacity increases with the increase of flow rate and slope.When the flow rate is 2 L/min,the sediment transport capacity is lower on the whole,and the increase range with the slope is not obvious.When the flow rate is 4 L/min and the slope is5～10°,the increase range of sediment transport capacity with the slope is 58%,when the slope is 10～20°,the increase range of sediment transport capacity with the slope is only 22% and 12%respectively.When the flow rate is 8 L/min and the slope is 5～10°,the sediment transport capacity increases by 64% with the increase of the slope,and by 27% with the increase of the slope when the slope is 10～15°.The sediment transport capacity hardly changes when the slope is 15～20°.When the slope is constant,the sediment transport capacity increases linearly with the flow rate,and the increase is more than 100%;（2）With the increase of erosion slope length,the sediment concentration of runoff increased gradually,and the rate of increase decreased continuously until the maximum sediment concentration corresponding to the sediment transport capacity was reached,and the sediment concentration of runoff reached saturation,then the soil would not be eroded any more.The attenuation coefficient of sediment concentration increases with the increase of slope is increases with the increase of flow rate and slope,which indicates that the slope length of the sediment concentration needed to reach saturation decreases with the increase of slopes and flow rates,and the attenuation coefficient almost does not increase when the slope exceeds 15 °,which indicates that the effective slope length of runoff eroded soil does not increase infinitely with the increase of slope;（3）The detachment capacity increases in different degrees with the increase of the slopes and the flow rates: when the slope is constant,the detachment capacity increases linearly with the flow rate,and the increase range is more than 100%,and the greater the slope,the faster the rate of increase;When the flow rate is 2L/min,the detachment capacity increases by 22%,55%and 33% with the increase of slope;when the flow rate is 4 L/min and the gradient is 5～15°,the detachment capacity increases by 83% and 47% with the increase of slope,and when the slope is 15～20°,the detachment capacity hardly changes;when the flow rate is 8L/min and the slope is 5～15°,the detachment capacity increases by 55% and 36%,respectively.When it is15～20°,it hardly changes;～（4）Based on the relationship between the measured detachment capacity and the sediment transport capacity,the sediment transport capacity under different slopes and flow rates is transformed into the expected value of the detachment capacity by the attenuation coefficient,and the calculated value of the detachment capacity is compared with the measured value by linear fitting.The slope of the straight line is 1.04,which shows that the expected value is close to the measured value;（5）We got that the rill erodibility of loess soil is 0.058 s/m and the critical shear force is1.55 Pa by fitting the linear relationship between denudation capacity and runoff shear force,which provides a basic reference for evaluating the ability of loess soil to resist erosion.