岷江老木孔航电枢纽库区泥沙淤积计算与分析

老木孔航电枢纽工程是岷江乐山-宜宾段航电梯级开发方案中的第一级,是以航运为主,航电结合的水利工程。首先建立平面二维水流泥沙数学模型,并由实测资料验证其相似性;再根据入库水沙资料,计算分析水库建成后不同时期的泥沙淤积量及其淤积分布,并初步分析分布不均形成的原因;讨论在各级频率洪水作用下,库区泥沙淤积对乐山城区及乐山大佛的影响;并分析泥沙淤积对库区建港环境的影响。通过物模实测值和数模计算值的比较,再次验证了该数学模型的适用性。结果表明:该数学模型可较好的模拟河段水流的运动及库区泥沙的淤积过程;泥沙淤积主要发生在老江坝尾至坝址河段,且估算了该段淤积量占淤积总量的85%;库区淤积后,频率洪水不会对乐山城区及乐山大佛产生影响。

CALCULATION AND ANALYSIS OF THE SEDIMENT DEPOSITION IN LAOMUKONG NAVIGATION-POWER JUNCTION ON THE MINJIANG RIVER

Laomukong navigation power junction is the first level of the navigation hydropower cascade development project located between Leshan and Yibin on the Minjiang River. It is a comprehensive water conservancy project which is based on shipping and integrated avionics, combining flood control, water supply, environmental protection and tourism. In this paper, a two dimensional mathematical model was established for sediment and river flow. The model consists of the flow equation, non equilibrium suspended sediment transport basic equation and the bed deformation equation. To prove the similarity, water level and cross section velocity distribution were verified based on the measured data. According to the water and sediment data of Laomukong, including the suspended particle gradation, bed load gradation and the scheduling mode of the reservoir, 3 representative years (low water 1971, ordinary 1979, ample flow 1985) were selected to constitute the cycle. The reservoir sedimentation in different periods was calculated after the completion of the reservoir. Based on the calculations, we analyzed the distribution of the sediment deposition, mainly about the sediment deposition and siltation thickness in the key parts. Then a preliminary analysis was made on the reasons of sediment uneven distribution and the relationship between sediment and scheduling mode of reservoir. Due to the aggradation of the reservoir, it is necessary to discuss how the change of reservoir level affects on Leshan city and the Leshan Giant Buddha in different flood frequencies. According to the computation of sedimentation, an analysis was made on the influence of reservoir sedimentation on port construction environment. The comparison of the values of physical model and numerical simulation indicated that the two dimensional mathematical model for sediment could well simulate the process of sediment deposition in the reservoir. The results of the paper showed that: (1) the model can simulate the movement of water flow and the process of sediment deposition; (2) the sediment deposition mainly occurred in the reaches between Laojiangba and Laomukong, and the sedimentation volume accounted for 85 percents of the total; (3) after the sedimentation in the reservoir, flood in different frequencies does not have an impact on Leshan city and Leshan Giant Buddha