水保所知识产出(1956---)知识库

为探明降雨条件下黄土急陡坡坡面薄层水流水力学特性，采用室内模拟降雨的方法，
研究了6个坡度（25°、30°、35°、40°、45°和50°）和3个雨强（1.0 mm min -1 、1.5 mm min -1
和2.0 mm min -1 ）组合条件下坡面薄层水流水力学参数的变化规律。结果表明：（1）坡度相同时，流
速随雨强的增加而增大；雨强相同时，坡度对薄层水流流速的影响存在临界效应（40°～45°），小
于临界坡度，流速随坡度的增加而增大，大于临界坡度，流速随坡度增加而减小。（2）各坡度条件
下，坡面薄层水流的平均径流水深随降雨强度增加呈平稳增长趋势；相同雨强时，径流深随坡度的增
大有减小趋势。（3）黄土急陡坡坡面雷诺数（Re）整体较小（远小于580），试验条件下坡面薄层径
流属于层流且水流处于层流中的失稳区；弗劳德数（Fr）大于0.8，薄层水流属于急流。（4）阻力系
数（f）随着降雨强度增加而增大，随着坡度的增加而减小。（5）方差分析结果显示，雨强、坡度及
二者交互作用对急陡坡坡面薄层水流水力学参数均有显著影响（p<0.01），但流速、弗劳德数和阻力
系数的变化主要受坡度控制，而径流深和雷诺数的变化主要受雨强控制。

【Objective】Hydraulic characteristics of shallow flow are essential to elucidating
mechanisms of soil erosion and sediment yield on the slope. However, most of the studies in this as-
pect have been reported on slopes less than 25°in gradient. This paper is oriented to study hydraulic
characteristics of steep loess slopes（25°～50°）, in an attempt to lay down a foundation for elu-
cidating in-depth relationships of the hydraulic characteristics of shallow water flow on slopes with
slope soil erosion.【Method】An indoor experiment was carried out simulating rainfalls on steep loess
slopes. The experiment was designed to have only one soil type（loessal soil）, three rainfall intensity
（1.0 mm min -1 , 1.5 mm min -1 and 2.0 mm min -1 ）and six slope gradient（25°, 30°, 35°, 40°, 45° and
50°）with the aid of perforated metal flumes（3 m in length, 1 m in width and 0.30 m in depth）. Runoff,
sediment and flow velocity on the slopes were observed, relative to rainfall intensity and slope gradient.
【Result】Results show:（1）Flow velocity increased with rising rainfall intensity on slopes the same in
gradient, and under the same rainfall intensity, the effect of slope gradient on flow velocity exhibited a crit-
ical point in gradient, that is, between 40°and 45°under the same rainfall intensity. On slopes with gradient
lower than the critical point, flow velocity increased with rising slope gradient, whereas on slopes with gra-
dient higher than the point, flow velocity decreased with rising slope gradient. （2） Mean runoff depth in-
creased steadily with rising rainfall intensity on all slopes regardless of gradient; but decreased with rising
slope gradient under rainfalls the same in intensity. （3） Reynolds numbers of steep loess slopes were on
the whole relatively small, often far below 580. In this study shallow flows on slopes were of laminar flow
in destabilized layers, while shallow flows with Froude number beyond 0.8 were of rush. And （4） Dar-
cy-Weisbach resistance coefficient （f） was positively related to rainfall intensity and negatively to slope
gradient. 【Conclusion】Rainfall intensity, slope gradient and interactions between these two factors all
have significant effects on hydrodynamic parameters （p<0.01） of shallow flow on steep slopes, but flow
velocity, Froude number and Darcy-Weisbach resistance of the shallow flow varied mainly with slope gradi-
ent, while runoff depth and Reynolds number did mainly with rainfall intensity.