植物坝前上游段推移质泥沙的输移特性

Transportation characteristics of bed load sediment of upper reaches end before vegetation dam

通过室内水槽模型试验,研究了植物坝对水流流态及坝前上游段推移质泥沙输移的影响,试验是在1/150,1/100和1/50三种底坡下均对应5.09,9.08,13.08L·s-1三种流量时进行观测的。由试验得出,植物坝可以引起上游水位壅高,水流流速减小。加沙后,上游段推移质泥沙的运动速度明显减小,大量粗颗粒泥沙在坝前淤积下来,说明植物坝具有较好的阻水拦沙作用。输移过程中,泥沙群前端最初呈三角形分布,越靠近坝体,三角形分布越不明显,说明坝前壅水及速度梯度的存在使泥沙的输移形态发生了变化。还证明底坡对泥沙的输移分布形态及运动速度影响很大,从理论上分析了植物坝前上游段进口断面输沙率与推移质泥沙运动速度之间的关系。

By the indoor flume model experiment, this paper studies the influence of vegetation dam on flow pattern and bed load sediment transportation of upper reaches end before the dam. The experiment was done under 1/150, 1/100 and 1/50 three base slopes with 5.09 L·s^(-1), 9.08 L·s^(-1) and 13.08 L·s^(-1) three discharges. The experiment showed that vegetation dam can cause backwater of upper reaches and reduce flow velocity. After add in sediment, bed load sediment's kinematic velocity of upstream is reduced obviously. And it makes much coarse-grained sediment deposit before the dam. This shows that vegetation dam can retard water and sediment. In the process of transportation, sediment group leading end appears triangle distribution at first. And when more and more it nears the dam body, the triangle distribution disappears gradually. This shows that backwater and velocity gradient change the feature of sediment transportation. And it proves that base slope has prodigious influence on the feature of sediment transportation and sediment kinematic velocity. Finally, we analyzed theoretically the relations between inlet section sediment discharge and bed load sediment's kinematic velocity of upper reaches before the dam.