长江三峡水利枢纽坝区河势研究

Studies on reservoir sedimentation in TGP damsite river stretch

本文介绍水库泥沙淤积过程的基本规律,如泥沙粒径的分选现象、库区淤积的基本形态、由淤积初步平衡到达输沙平衡经历的“淤粗悬细”过程,以及三峡水库悬移质淤积过程的特点,如淤积形态为三角洲淤积,初期排沙比大,变动回水区的淤积比值小、达到初步平衡的年限很长等。三峡工程坝区系宽谷河段,包括庙河至伍相庙连续微弯段和三斗坪、乐天溪弯道段,没有急弯和窄浅河段。根据分析计算和长系列泥沙模型试验成果,三峡水库悬移质泥沙淤积达到初步平衡阶段,汛期限制水位运用时,坝上游河势尚较蓄水前平顺,曲溪口至太平溪、太平溪经伍相庙至祠堂包山咀,将不出现蓄水前的连续急弯;坝区主河槽的断面面积应约为30000m^2左右,最小库面宽度约1200m;当流量56700m^3/s 时,最大水面流速应小于3.52m/s;水力要素与长江武汉河段基本相同。

This paper presents the basic laws of the process of reservoir sedimentation such as the sorting phenomena of the the grain sizes of sediment,the fundamental patterns of reservoir sedimentation and the process of“depositing the coarser and sus- pending the fine”which predominates the variation from the stage of the preliminary e- quilibrium of sedimentation to the state of equilibrium of sediment transport,and the features of the sedimentation process of the suspended load in the Three Gorges Reser- voir,such as the delta deposit being the pattern of sediment accumulation,the large sediment delivery ratio in the early stage,the small sedimentation ratio in the fluctuat- ing backwater region and the long dur ation needed to reach the preliminary equilibri- um,etc. The dam area of the Three Gorges Project is a river stretch with wide valley with no abrupt bend and no narrows and shallows,including the reach of the continuous slight bends from Miaohe to Wuxiangmiao and the reaches of Sandouping bend and Letianxi bends.Based on the results of the analyses the calculations and the long series of experiments of the sedimentation models,it was found that after the accumulation of the suspended load in the Three Gorges Reservoir has reached the preliminary equibri- um stage,when the reservoir is operated at the flood limit level,the river regime up- stream of the dam will be more gentle and smooth as compared with the condition be- fore the reservoir filling,in the reaches from Quxikou to Taipingxi and from Taipingxi through Wuiangmiao to Citang—Baoshanzui there will be no longer successive bends as occurred before the reservoir filling;and that in the dam area the cross sectional area of the main channel will be about 30000m^2,the minimum width of the reservoir surface will be about 1200m,when the discharge is 56700 m^3/s,the maximum surface veloci- ty will be less than 3.52m/s;and the hydraulic elements are basically the same as those of the Wuhan reach of the Yangtze River.