三峡大坝—葛洲坝河段水沙变化及冲淤特性

掌握三峡和葛洲坝枢纽间河段水沙及冲淤特性的变化规律，是河段诸多工程问题研究的前提。对大量水沙地形资料进行分析，探讨泥沙起动理论在冲刷预测中的应用。长江上游水库建设及两大枢纽相继运行，河段年径流量微减，月均流量发生"削峰填谷"重分配，年输沙量大幅降低，河段水沙关系显著改变；河段累积冲淤量受极端水文条件和枢纽调度的短期和长期控制，时间上具有明显阶段性特征，空间上则表现为部分子河段的活跃性；床沙组成随枢纽运行先后发生细化和粗化；基于沙玉清起动流速公式绘制了起动临界条件曲线图，通过推算断面最大可动床沙粒径或临界流量，可为河床冲刷可能性的预判提供参考。

Variation in water and sediment conditions and erosion and deposition characteristics in the reach between Three Gorges Dam and Gezhou Dam

A correct understanding of the variation pattern of water and sediment conditions as well as erosion and deposition characteristics in the reach between Three Gorges Dam and Gezhou Dam is essential for studying the many engineering problems in the reach. In this study,abundant water-sediment topographic data were analyzed,and the application of the theory of sediment incipient motion in erosion prediction was discussed. Owing to reservoir construction in the upper reaches of the Yangtze River and the successive operation of the two major hubs,the annual runoff in the reach was slightly reduced,the monthly average runoff was redistributed by "peak load shifting," the annual sediment discharge declined considerably,and the water-sediment relationship in the reach was significantly changed. The cumulative erosion and deposition quantity in the reach was under short- and long-term control by the extreme hydrological conditions and scheduling of the hubs. In terms of time,there were apparent phased characteristics;in terms of space,some sub-reaches were in an active state. The bed sediment was refined and coarsened successively with the operation of the hub. The incipient critical condition curve was drawn based on Sha's incipient velocity equation,and the estimation of the maximum particle size of movable bed sediment or critical water flow of the cross-section provided a reference for predicting the possibility of riverbed erosion.