模拟降雨条件下红壤坡面侵蚀产沙水动力学特征

目的]对红壤坡面侵蚀过程中的产流、产沙以及坡面径流水动力学参数进行试验研究,为揭示红壤坡面侵蚀产沙机理提供科学依据。方法]以我国南方侵蚀性红壤为研究对象,采用人工模拟降雨法,通过不同坡度(6°,10°和15°),不同雨强(120,180和240 mm/h)条件下的模拟试验分析红壤坡面产流产沙过程及径流水动力学特征。结果]在坡度一致时,坡面累积径流量和累积产沙量均随雨强的增大而增大,径流率表现为初期的波动增长,随降雨进行逐渐达到稳定状态,且径流率随坡度增大而增大;坡面产沙过程受坡度和雨强的双重影响;侵蚀产沙率呈降雨初期急剧上升,随后迅速下降并趋于平稳的趋势。试验坡面的径流水动力学特征表明,阻力系数f与雷诺数R_e无明显的相关关系,但与弗洛德数F_r存在显著的指数关系。结论]径流水动力学参数与侵蚀产沙量之间存在明显相关关系,相比较而言,径流雷诺数R_e与坡面侵蚀产沙量间的关系最密切。

Hydrodynamic Characteristics of Runoff in Red Slope Erosion Process Under Simulated Rainfall Experiments

Objective] The experimental studied runoff yield, sediment yield and runoff hydrodynamic parameters during erosion process of red soil slope in order to provide the basis for revealing the mechanism of slope erosion and sediment yield on red soil slope.Methods] Red soil was used, a total of 18 rainfall simulation experiments were conducted in a 8.0 m long drainable flume, with treatments including three levels of typical slope gradients (6°, 10°,15°) and three rainfall intensities (120, 180, 240 mm/h). The processes of runoff generation, sediment yielding, and runoff hydrodynamic characteristics variation were analyzed.Results] The accumulative runoff and sediment load significantly increased with the increasing of rainfall intensity under the same slope gradient. The runoff rate variation showed a steady state after an initial increased fluctuation. The sediment yield rate increased with the increases of both rainfall intensity and slope gradient. The sediment generation process showed a variation that increased rapidly at the beginning and decreased quickly with the experiment time passed. There was a good exponent relationship between Froude numbers and Reynolds numbers, while flow Darcy-Weisbach friction coefficients and Reynolds numbers had no obvious correlation.Conclusion] There is a significant correlation between runoff hydrodynamic parameters and erosion sediment yield. By comparison, Reynolds number of runoff is the most closely related to slope erosion sediment yield.