三峡水库挖粗沙减淤研究

Reducing Deposition in TGP Reservoir by Dredging Coarse Sediment

针对三峡水库运行后期存在的泥沙问题,提出在水库变动回水区固定河段进行较大规模挖粗沙减淤的方法,冀以减少水库后期淤积,保障三峡工程长远利用,持续发挥综合效益。分析了当前的挖泥技术和建筑河砂的市场情况,认为现在开始在三峡水库较大规模挖取粗沙已经比较经济,具有相当的可行性和必要性。采用一维不恒定水流泥沙数学模型,对20世纪60年代(60s)和90年代(90s)水沙系列方案进行计算。将0.1mm以上泥沙作商业粗沙,按固定河段连续挖泥方式,水库运行到100年时,按三峡设计泥沙系列(60s)减淤量可达37亿m3,按三峡蓄水前最近泥沙系列(90s)可减淤27亿m3。百年淤积总量可控制在140亿m3(60s)或110亿m3(90s),挖泥减淤效率达到100%。这对保护三峡水库后期效益、特别是防洪库容长期利用具有很大作用。笔者认为三峡水库挖泥减淤途径基本可行,值得深入研究。这一减淤方式也可为其他河道型水库淤积控制提供参考。

A scheme of deposition control for the reservoir of Three Gorges Project （TGP） by dredging the coarse sediment at fixed reaches in the fluctuating backwater reaches is studied this paper. With the increasing capacity of dredging promoted by fast development and commercial needs of dredgers and large scale dredging projects, and the market of river-sand along the Yangtze, in particular, in recent decades, it is shown that reservoir dredging is not as expensive and low efficient as it was previously believed and large scale dredging for reservoir de-siltation seems to be worthy of consideration. Applying a well-applied model of unsteady flow and sediment transport, the authors studied many cases with respect to different flow and sediment conditions. Computation results reveal that 100 years accumulated deposition after dredging is to be decreased by 20%, and dredging and intercepting coarse sands are proved to be highly effective. This scheme may become a sustainable way for TGP to keep a low level of deposition and to protect its flood control capacity. This scheme may also serve as a reference for de-siltation of other river shaped reservoirs.