Abstract: The fine sediment deposition in the permanent backwater zone of the Three Gorges Reservoir has exceeded its predictions made during its design period. A series of laboratory experiments were done on samples of fine sediment from the typical part of Huanghuacheng in the Three Gorges Reservoir. Compared with the 4 existing formulas, an improved incipient velocity function for fine sediment deposit was developed including its influence of water pressure and molecular force, and a 2D hydrodynamic-morphological model for simulating channel evolution processes was improved according to the movement of the physical movement of local fine sand. The proposed velocity formula was considered in calculating fine sediment transport, and the improved 2D numerical model applied in Huanghuacheng. Comparisons between model simulation results and field measurements were in agreement. The result shows that the 2D model can predict fine sediment behavior and assist navigation management decisions in the permanent backwater region mentioned above.

Key words: waterway engineering, fluvial process, fine sediment behavior, braided river, numerical simulation, incipient velocity

摘要： 三峡水库蓄水以来，常年回水区部分河段细沙淤积幅度远远超过论证阶段的研究成果。采用典型分汊河段(忠县黄花城)的细沙样本进行了临界起动条件的水槽试验；根据4 种现有细沙起动流速公式建立了考虑水压力与分子力的、适应于三峡库区的细沙起动流速公式；考虑了三峡库区细沙运动的物理过程，对现有平面二维水沙模型的细沙模块控制方程源项进行了改进；采用改进后的细沙模块对黄花城分汊河段的冲淤过程进行了模拟，对比分析了黄花城河段断面流速分布、细沙冲淤变化以及断面地形变化的模拟值与实测值。结果表明：改进后的细沙模块能够较为准确地反映三峡库区河道细沙输移过程；可将改进后的平面二维水沙数值模型应用于三峡库区细沙河道的冲淤预测中，为航道治理维护提供参考。

关键词: 航道工程, 河道演变, 细沙输移, 分汊河段, 数值模拟, 起动流速