坡面流挟沙力计算公式及其评价

Equations and evaluations of sediment carrying capacity of overland flows

坡面水流挟沙能力的计算是土壤侵蚀过程中最为重要的一环,它是判别坡面是否发生冲淤的依据。本文总结了现有的坡面流挟沙力计算公式,并利用实验数据对各公式的适用性和局限性进行了评价。结果表明:Low和Abrahams公式只有在不考虑降雨的情况下可以较好地预测坡面流挟沙力;Shih公式虽然考虑了降雨影响,但只适用于特定的水力条件;Guy公式将挟沙力分为坡面流贡献和降雨贡献两部分,用实验数据重新率定参数后,能更好地预测坡面流挟沙力。此外,临界Shields数作为泥沙颗粒启动的判别条件在降雨影响下不再适用于坡面流。

Estimating sediment carrying capacity of overland flow is the key point in soil erosion process and it is also the criterion to decide whether erosion or deposition happens. The existing sediment carrying capacity equations are summarized and evaluated by using the laboratory data. Results show that Low and Abrahams equations can give good predictions without rainfall impact. Although the rainfall impact is considered, Shih equation performs well only under special hydraulic conditions. Guy equation separates the portion of sediment carrying capacity due to flowing water from that due to rainfall impact. New parameters of Guy equation are obtained through calibration and better predictions of sediment carrying capacity are given. The criterion of critical Shields number for sediment inception is not applicable for overland flows under rainfall impact.