坡面侵蚀产沙与水力学特征参数关系模拟

坡面侵蚀产沙主要受坡面径流动态过程的影响,表征坡面径流过程特征是水力学特征参数。为了研究坡面侵蚀产沙与主要水力学特征参数的关系,揭示坡面侵蚀产沙的水动力学机理。采用人工模拟降雨的方式,通过不同坡长和雨强的组合试验,基于跨雨强和跨坡长的综合性分析的思路,应用经典水力学计算和统计拟合相结合的方法,对特定坡度(20°)下,5个坡长(1,2,3,4,5m)13个降雨强度的试验监测数据进行了分析。结果表明:(1)在设计雨强(0.65~2.0mm/min)和坡度范围内,坡面径流都属于缓流,雨强0.7mm/min都为层流,呈现紊流的最小雨强为1.01mm/min;(2)坡长对弗汝德数和阻力系数的影响较大,对剪切力、径流深和雷诺数的影响很小,3m坡长是坡面径流过程的波动步长,是模拟试验研究坡面径流水动力学参数的最小设计坡长;(3)流速是坡面侵蚀产沙的主要影响参数,剪切力是判断坡面侵蚀产沙强度的综合性指标之一。这些研究结论为实地大范围通过径流量和流速来预测侵蚀产沙的强度提供了简便快速的判断方法。

Research on Relationships Between Sediment Yield and Hydraulics Parameters on Slope

The slope erosion and sediment yield are mainly affected by the dynamic process of slope runoff.The characteristics of slope runoff process are described by hydraulic parameters.The purpose of this paper was to study the relationships between slope erosion and sediment yield and hydraulics parameters,and to reveal the hydrodynamic mechanism of slope erosion and sediment yield through artificial rainfall simulation.The principles of classical hydraulic calculation and statistical fitting were applied for the comprehensive analysis of runoff and sediment yield process in different rainfall intensities and slope lengths.Five slope lengths (1,2,3,4,5 m) with 13 rainfall intensities were designed under a specific slope (20°).The conclusions were listed as follows:(1) Within the designed rainfall intensities (0.65 ～ 2.0 mm/min) and slope (20°),slope surface runoff were slowly,which was laminar flow under rainfall intensity ＜ 0.7 mm/min,the smallest rainfall intensity of turbulent flow occurrence was 1.01 mm/min.(2) The influence of the slope length on the Froude number and resistance coefficient were larger than on the shear stress,runoff depth and Reynolds number.The slope length of 3 m was the step length of slope runoff fluctuation,and was the shortest slope length designed for a simulated experiment of hydrodynamic parameters.(3) The velocity was the main influence parameter of slope surface erosion and sediment yield,and the shear stress was one of comprehensive indicators for estimating the strength of slope surface erosion and sediment yield.The above results provided a simple and rapid judgment method for predicting the intensity of erosion and sediment yield through runoff and flow velocity in wide field.