坡面降雨径流侵蚀输沙的不平衡特性研究

Study on Unbalance Characteristics of Sediment Transport by Rainfall Runoff Erosion on Slope

针对降雨和床面大糙度共同作用下坡面降雨径流侵蚀不平衡输沙特性研究薄弱的问题,采用室内模拟降雨试验的方法,研究不同降雨强度和坡长条件下的坡面降雨径流侵蚀输沙特性。结果表明:(1)坡面为裸坡、坡度为10°条件下,径流含沙量随坡长的增加呈增大趋势,当坡长由1 m增加至8 m时,同一雨强下径流含沙量增大3.28~7.15倍;径流含沙量随雨强的增大而增加,当雨强由40 mm/h增大至120 mm/h时,同一坡长下径流含沙量增加1.41~2.97倍。(2)分析降雨径流侵蚀条件下,水动力学参数对坡面径流挟沙能力的影响发现,水流挟沙能力与流速的3次方成正比,与水力半径和沉速的乘积成反比,得到降雨条件下的水流挟沙能力计算公式。(3)研究坡面降雨径流侵蚀输沙的不平衡特性表明,雨强与恢复饱和系数之间呈幂函数关系,给出坡面不平衡输沙模型并进行验证,表明该模型可以较好地模拟坡面降雨径流侵蚀输沙沿程变化。研究结果可为预测坡面径流侵蚀输沙沿程变化及完善坡面径流侵蚀机理提供参考。

In view of the weak research on the unbalanced sediment transport characteristics of rainfall-runoff erosion under the combined action of rainfall and bed roughness,the variation characteristics of rainfall-runoff sediment transport under different rainfall intensities and slope lengths were studied by using the indoor simulated rainfall test.The results showed that:(1)Under the condition that the slope was a bare slope and the slope was10°,when the slope length increased from 1 m to 8 m,the sediment concentrations of runoff increased by 3.28~7.15 times under the same rainfall intensity.The runoff sediment concentrations increased with the increase of rainfall intensities.When the rainfall intensities increased from 40 mm/h to 120 mm/h,the runoff sediment concentrations increased by 1.41~2.97 times under the same slope length.(2)According to the existing formula of sediment carrying capacity of river channel,after analyzing the influence of rainfall,slope,slope length and other factors on runoff sediment carrying capacity,and based on the rainfall test data and collected test data,the formula of sediment carrying capacity under rainfall condition was obtained,which could be applied to the calculation of sediment carrying capacity of overland flow under rainfall condition.(3)The influence of rainfall intensity on restoring saturation coefficient was discussed,and the unbalanced sediment transport model was proposed and verified.The verification results showed that the model had a good simulation effect on the variation of rainfall runoff sediment concentration along the slope.These results could provide reference for predicting the variation of sediment concentrations along the slope runoff and improving the erosion mechanism of thin layer runoff.