恒定流中非均匀沙推移质不平衡输沙研究

Study on Noneqilibrium Nonuniform Bedload Transport by Steady Water Flow

冲积河流的平衡状态指的是在足够长的时间内(以月计)进入某一河段的泥沙等于从该河段输出的泥沙。恒定流中,由于泥沙输移率随时间及空间变化,因此,泥沙的输移总是不平衡的。我们选用粒径为0.05～20.00mm的煤屑及天然沙。在长30m、宽0.5m的变坡水槽内进行了清水冲刷(恒定流)推移质不平衡输沙试验;建立了恒定流中非均匀沙推移质不平衡输沙方程;在修正Gessler,J.冲蚀物级配基础上,提出了推移质级配的计算公式;河床质级配方程采用CARICHAR混合层模塑;并将推移质输沙、级配方程及河床质级配方程应用于河床粗化数学模型,得到计算与水槽实测相一致的结果。

With stesdy water flow an equilibrium state for an alluvial reach exists when the input of sediment over a sufficiently long time(time interval of the order of months)is equal to the outqut of sediment A noneqilibrium state exists under steady water flow when the sediment transport rate changes with time and with position, so that there is no blance between input and output of sediment.The experiments were preformed in a 30m open circuit tiltung flume with the bed slope=0.00 0 009 and flume width 0.5m. The boundary conditions in all experiments were as follows: the rate sediment supply at the upstresm end was zero. The bed material was coal and sand in the river. The rain diameter of the bed materialwas the range of 0.05—2.00mm. The equation of noneqilibrium onuniform bedloa continuous transport is derived. The grain distribution of the nonuniform bedload is calculated by modifying Gessler's formula. The grain—size distribution of bed material is calculated by CARICHAR mixed layer model.These Eqs are applied to numerical simulation of armoring of riverbeds. The results of the transport rate and the grain size—distribution of the bedload at the end of the downstream in the process of time, and the grain size—distribution of the bed material in the process of time and distance are all in close agreement with the measurements.