信江八字嘴枢纽坝下冲刷计算研究

Study on Calculation of Scour downstream the Dam of Bazizui Hub of Xinjiang River

针对枢纽下游河床冲刷这一水利航运界普遍关注的工程问题,为确保信江八字嘴航电枢纽工程的安全及下游通航条件,基于信江水文基本特性、河床演变特性分析,建立平面二维水沙数学模型,对八字嘴枢纽建成运行后可能引起的坝下冲刷进行了计算研究。结果表明:工程河段地处鄱阳湖影响范围,天然情况下洲滩小幅淤长,河道演变较为稳定,但近年来部分区域频繁的采砂活动造成局部河床显著下切,需要引起高度重视;经过10个水文年冲淤调整后,西大河坝下5 km范围内因大规模采砂作用河床深凹、水深较大,故冲刷幅度相对不大;坝下5～10 km范围冲刷较为明显,冲刷部位主要在河槽,平均冲刷深度约为0. 29～0. 93 m,边滩部分变化很小;东大河由于下游双港枢纽的抬水作用,坝下冲刷幅度整体较小。总体来看,八字嘴枢纽坝下河床冲淤变化的幅度随时间逐渐减小,河道河势基本保持稳定。

As the scour of the downstream river bed of navigation and hydropower project is an engineering problem of wide concern,a 2-D water-sediment mathematical model is established herein on the basis of the analysis on both the basic hydrological characteristics of Xinjiang River and the evolution feature of its bed,and then the possible downstream scour of the dam for the project to be caused after the complete of Bazizui Navigation and Hydropower Project is calculated.The result shows that the scour is more obvious within the range of 5~10 km of the downstream river reach of the project,while the scoured locations are mainly concentrated inside the river channel;for which the mean scouring depth is to be 0.29~0.93 m and the variations of both the side shoals are less after 10 hydrological years,while the amplitude of the scouring and silting evolution of the river bed is to be gradually decreased with the time,thus the river regime is to basically remain stable.