饱和与非饱和黄绵土细沟径流水动力学特征及侵蚀阻力对比

Comparation of Hydrodynamic Characteristics and Flow Resistance Under Rill Erosion Between Saturated and Unsaturated Loess Soil

近地表水文状况显著影响坡面土壤侵蚀过程。土壤饱和状态作为一种特殊的近地表水文状况,其细沟侵蚀特征较之非饱和状态存在明显的差异。以黄绵土为研究对象,采用限定性细沟模拟冲刷,对比研究了饱和与非饱和状态下黄绵土的水动力特征和侵蚀阻力。结果表明:饱和黄绵土径流流速与坡度、流量之间符合良好的幂函数关系,坡度对流速的影响更甚;饱和黄绵土径流流速约为非饱和黄绵土的1.17倍,其坡面摩擦阻力仅为非饱和黄绵土的70.3%;同种工况下,非饱和黄绵土的径流含沙量和细沟径流动能明显偏低,随着径流动能增大,2种土的径流含沙量均呈现对数型增长,径流含沙量峰值稳定在400,280kg/m^3内;饱和与非饱和黄绵土的细沟可蚀性参数分别为0.088,0.057kg/(m^2·s),相应的土壤临界剪切力分别为0.773,1.561Pa,表明饱和黄绵土更易剥蚀、流失。

The hydrological condition of the near surface plays a vital role in the slope soil erosion process.The characteristics of soil erosion in saturated soil were different from that in unsaturated loess soil.In the study,loess soil was adopted in the well-defined rill simulation scouring experiment to explore the different hydrodynamic characteristics and flow resistance between saturated and unsaturated soil conditions.Results showed that the rill flow velocity of saturated soil had good power function with slope gradient and flow rate,and the slope gradient had a greater impact on the velocity.The rill flow velocity of saturated soil was about1.17 times that of unsaturated loess soil,while the friction resistance of slope surface under saturated state was only 70.3%compared with that in unsaturated condition.Under the same conditions,the rill flow energy and sediment concentration of unsaturated soil were much lower than those of saturated soil.With the increase of rill flow energy,the sediment concentration of both kinds of soil showed a logarithmic growth,and the peak value of rill flow sediment concentration was stable at about 400 and 280 kg/m^3,respectively.Saturated and unsaturated loess soil erodibility parameters were 0.088 and 0.057 kg/（m^2·s）,and the critical shear stress were 0.773 and 1.561 Pa correspondingly,indicating that saturated soil was much easier to be dispersed and eroded by water.