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水库修建后,清水下泄将造成坝下游河道处于冲刷状态,引起河势调整,给下游防洪、水资源利用及航运等可能带来一系列不利的影响;由于坝下游清水冲刷过程的复杂性,沙质河床含沙量沿程恢复规律一直是河流泥沙动力学的难度问题之一.基于此,首先本文根据湍流猝发理论推导出清水冲刷下沙质型河床含沙量沿程恢复的理论公式,然后利用配置精密仪器的变坡水槽试验进行相关研究,并根据试验数据分析不同条件下垂线平均含沙量沿程恢复的特性.试验成果显示,当流量、床沙粒径不变,河床比降为0.5‰、1.0‰与2.0‰时,垂线平均含沙量恢复过程差异性较小,但随着冲刷距离发展α_1(近底处含沙量与垂线平均含沙量比值)递减而α_2(近底处挟沙能力/垂线平均挟沙能力比值)略有增加,且在清水冲刷发展过程中α_1是一个逐渐靠近α_2的动态变化过程;当床沙粒径与河床比降不变,流量越大,水流垂线平均含沙量恢复饱和的数值与距离越大,α_1、α_2数值同样也越大;当流量、河床比降不变,床沙粒径颗粒越细,含沙量恢复饱和时的数值越大,恢复距离也越长,反之亦然.
After the reservoir is constructed, the release of clean water will cause the downstream channel of the dam to be washed off, causing the adjustment of the river regime, which may bring a series of unfavorable influences to downstream flood control, utilization of water resources and shipping. Due to the complexity of the process of water flushing downstream of the dam, Based on this, firstly, based on the theory of turbulent burst, this paper deduces the theoretical formula for the sediment sediment recovery along the sandy river bed under the condition of clean water scouring, and then According to the experimental data, the characteristics of the average vertical sediment concentration under the different conditions were recovered.The experimental results show that when the flow rate and bed sand particle size are constant, the riverbed ratio is reduced to 0.5 ‰, 1.0 ‰ and 2.0 ‰, the discrepancy of average vertical sediment concentration was small, but with the development of scour distance α_1 (the ratio of sediment concentration at near bottom and vertical sediment) decreased and α_2 ( The sediment carrying capacity near the bottom / the average sediment carrying capacity of the vertical line) increased slightly, and α_1 was a dynamic process gradually approaching α_2 during the process of clean water erosion. When the bed size and bed ratio The same value of α_1 and α_2 is also obtained when the flow rate and river bed ratio are the same, the finer the particles of bed sand, The greater the numerical value when the sediment concentration is saturated, the longer the recovery distance, and vice versa.