深水库区细颗粒淤积物重力驱动流动数值模拟——以三峡水库为例

Numerical simulation of gravity-driven motion of fine-grained sediment deposits in large reservoirs: case study of the Three Gorges Reservoir

针对三峡水库近坝区细颗粒泥沙淤积特征,从过程机理出发,提出了深水库区细颗粒泥沙淤积过程的物理图形。采用临界坡度作为细颗粒淤积物失稳流动的判别标准,借鉴浅水流动模式,描述失稳后细颗粒淤积物重力驱动流动过程,通过耦合三维水沙数学模型,建立了细颗粒淤积物重力驱动流动的数值模拟方法,在此基础上对三峡水库近坝区细颗粒泥沙淤积形态进行了模拟研究。研究结果表明:水库蓄水运行初期近坝区细颗粒泥沙主要淤积在断面深槽内,且呈水平状,考虑重力驱动流动后的模拟结果与实测结果吻合较好,从而为进一步深入研究深水库区细颗粒泥沙运动特征提供了技术支撑。

Sediment deposition is one of the key issues during the processes of reservoir construction and operation.On the basis of the observed sedimentation patterns in the dam area of Three Gorges Reservoir（ TGR）,a schematic diagram of fine-grained particles sedimentation in the dam area was proposed. Critical slope was used to judge the incipient motion of the fine-grained deposits. It was assumed that the mass transport processes of fine-grained deposits were dominated by the shallow flow equations. A numerical method of gravity-driven motion of fine-grained deposits was developed and combining with a 3-D flow and sediment transport model. Then,the sedimentation patterns of finegrained particles in the dam area of the TGR were simulated by the developed method. The simulated results agreed well with the measured data. Sediment deposits in the dam area are mostly found at the bottom of the main channel,which have reshaped the river bed with a flat surface that is nearly horizontal. In contrast,very little fine sediment deposits can be found on the bank slopes of the channel. The developed method can be applied to improve our understanding of fine sediment transport mechanisms in large reservoirs.