极缓坡黄土坡面片状侵蚀及其水动力学参数特征

Sheet erosion and its hydrodynamic parameters of extremely gentle loess slopes

随着黄土高原生态文明建设的持续开展,极缓坡耕地成为当地受生产活动影响最显著的区域,其土壤侵蚀规律应得到关注。基于此,采用室内模拟降雨试验,在90 mm/h雨强、两种坡度(2.5°和5°)和两种坡长(5 m和10 m)情况下,对两种土壤(安塞土和绥德土)的片状侵蚀特征及水动力学参数的变化规律进行了研究。结果表明:与安塞土相比,绥德土的产流和径流增加速度快,有较高径流率和含沙量,且易发生细沟。安塞土在径流稳定前的平均径流率和含沙量的变化范围分别为2.76~8.61 L/min和0.80~9.26 g/L,径流稳定后两者的变化范围分别为3.76~11.69 L/min和0.46~2.88 g/L;绥德土径流稳定前后平均径流率和含沙量的范围分别为3.94~12.75 L/min、2.13~10.64 g/L和4.51~15.02 L/min、1.20~4.51 g/L。两种土壤的含沙量与径流率的关系可以用线性递减函数和含沙量作为常数两种线性关系进行表征。雷诺数和径流功率与径流率呈明显稳定的线性递增函数关系;径流流速和弗劳德数随径流率增加有较明显的增加趋势,但波动性较大;径流剪切力随径流率变化表现出很大的离散性。总体上对于片蚀,雷诺数和径流功率是最能用以表征土壤侵蚀的水动力学参数,其次是径流流速和弗劳德数,再者是径流剪切力。研究结果可为优化土壤侵蚀模型参数提供理论参考。

With the continued development of ecological civilization on the Loess Plateau,cultivated land on the very gentle slopes has become the most significant area affected by local production activities,its soil erosion should be paid enough attention.Based on this,indoor simulated rainfall test is adopted to study the sheet erosion characteristics and the variation rules of hydrodynamic parameters of the two soils(Ansai soil and Suide soil)under the condition of 90 mm/h rainfall intensity,two slopes(2.5°and 5°)and two slope lengths(5 m and 10 m).The results show that,compared with the Ansai soil,the Suide soil has a shorter runoff production time,a faster runoff increasing rate,a higher runoff with sediment content,and is prone to rill erosion.The average runoff and sediment content of Ansai soil ranged from 2.76 to 8.61 L/min and 0.80 to 9.26 g/L before runoff stabilization,and from 3.76 to 11.69 L/min and 0.46 to 2.88 g/L after runoff stabilization.The average runoff and sediment content of Suide soil before and after runoff stabilization was 3.94 to 12.75 L/min,2.13 to 10.64 g/L and 4.51 to 15.02 L/min,1.20 to 4.51 g/L,respectively.The relationship between sediment content and runoff can be characterized by a linear descent function with sediment content as a constant.In contrast,the Reynolds number and runoff power increase linearly with runoff with a clear and stable behavior.The runoff velocity and Froude number show a clear trend of increasing with runoff,but the fluctuations are large.The runoff shear force shows a large dispersion with runoff.Overall,for sheet erosion,Reynolds number and runoff power are the most suitable hydrodynamic parameters to characterize soil erosion,followed by runoff velocity and Froude number,and runoff shear force.The above results can provide a theoretical reference for optimizing soil erosion model parameters.