黄绵土细沟水流输沙能力对地表冲刷流量的响应

为明确黄绵土在径流冲刷下的细沟侵蚀特征和产流产沙规律,通过细沟模拟,设计3个流量(2,4,8 L/min)和4个坡度(5°,10°,15°,20°),在变坡土槽中进行室内冲刷试验,实测不同坡度和流量下黄绵土在坡面细沟发育过程中产生的最大径流含沙量,并得到其相应的输沙能力(A)。结果表明,当坡度一定时,输沙能力随流量增大呈线性增大,且坡度越大增幅越明显;当流量较小时,输沙能力随坡度增加而缓慢增加,当流量达到8 L/min时,输沙能力随坡度增加的幅度更为明显,但坡度上升到15°以后几乎不再变化,说明流量对输沙能力的影响更为显著。含沙量(c)随沟长(x)的变化规律符合数学模型c=A(1-e-Bx),控制所有流量坡度组合在不同沟长(1,2 m)条件下进行冲刷试验,将冲刷测量得到的径流含沙量与各组合下的输沙能力(A)代入关系式,利用待定系数法计算出不同试验条件下含沙量随沟长变化的衰减系数(B)。研究结果可为黄绵土水土保持研究与实践提供理论基础与科学依据。

Response of Sediment Transport Capacity of Rill Flow to Surface Scouring Discharge in Loess Soil

To define the rill erosion characteristics and the law of runoff and sediment yield of loess soil in the process of rill development under runoff scouring, rill simulation test was conducted in variable slope soil troughs, and three flows (2, 4 and 8 L/min) and four slope gradients (5°, 10°, 15° and 20°) were set up. The maximum runoff sediment concentrations during rill development on the loess soil slope under different slopes and flows were measured, then its corresponding sediment transport capacity (A) was obtained. The results showed that, when the slope was constant, the sediment transport capacity increased linearly with the increasing of the flow rate, and the steeper the slope was, the more obvious the increase was. When the flow rate was low, the sediment transport capacity increased slowly with the increasing of the slope gradient. When the flow rate reached 8 L/min, the sediment transport capacity increased faster with the increasing of slope gradient, but it hardly changed after the slope increased to 15°, indicating that flow rate had more significant effect on sediment transport capacity. The trend of sediment concentration (c) with length of rill (x) conformed to mathematical formula c=A(1-e-Bx). We run a simulation by scouring the slope surface of 1 m and 2 m under all combinations of different slopes and flow rates we had set up, and the sediment concentration of runoff measured by scouring and the sediment transport capacity (A) under each combination were substituted into the formula, and attenuation coefficient (B) of sediment concentration varying with the rill length under different test conditions was calculated by method of undetermined coefficient. The results could provide theoretical and scientific basis for soil and water conservation research and practice in loess soil.