Study On Large-scale Gravel Dunes Movement Feature In The Upper Of The Yangtze River

There is distribution of a large scope of gravel navigation hindering reach in the upper reaches of the Yangtze River,especially the section of Yibin to Chongqing,some of where exists the significant gravel sand-wave movement.The large-scale gravel sand-wave in the upper reaches of the Yangtze River is the violent motion morphology of gravel bedload,having the size that reach to the same measuring order as that of the design water level of waterway,and could exert a great influence on the scale of shoals for waterway in the upper reaches of Yangtze River.The definitude of the large-size gravel sand-wave’s movement characteristics is closely related to the scientific determination of training program for the navigation hindering reach with gravel sand-wave.However,there are few studies on the movement characteristics of large-scale gravel sand-wave movement for large mountain rivers,whose the timing,conditions,scale and speed of movement of the are difficult to be accurately predicted,and whose response relationship with the navigable conditions cannot be informed in time,all of which leads to that waterway training works is difficult to be performed and maintained,as a result,the Golden Waterway in the upper reaches of the Yangtze River are obstructed to play its benefits.Based on the physical model test of the Dongxikou waterway natural sand bed,the movement characteristics of the gravel sand-wave are studied in the respect of the relationship between the scale & propagation velocity of the gravel sand wave and the flow conditions.According to the observation data of gravel sand wave of Shaojibei,Pangxieqi and Doulizi beach in the upper reaches of the Yangtze River,the scale distribution and the movement characteristics of the large scale gravel sand wave are analyzed and the influence of gravel sand wave on the shoal for waterway as well the countermeasures were discussed in detail.The main studied contents and achievement of this paper are presented as following:(1)Based on analysis on the large amount of raw data in the upper reaches of the Yangtze River,the movement and scale characteristics of large scale gravel sand wave have been obtained.Combined with the physical moving bed model experiment,the discriminant expression of gravel sand wave morphology has been verified.The study shows that the large scale gravel sand wave in the upper reaches of the Yangtze River is basically in the sand ridge stage.(2)The study of movable-bed physical model experiments suggests that the wave height of large-scale gravel sand wave can achieve better results when using the existing formula for calculating,while the expression of wavelength,slope ratio and advance velocity of sand wave are not applicable.The relationship between the large-scale gravel sand wave and different parameters of water flow conditions as well that between the large-scale gravel sand wave and particle size of bed material have been analyzed by the single factor analyzing method,in which the expression of the wavelength,slope ratio and advance velocity of sand wave of large scale gravel sand have been worked out.In line with the measured data from the upper reaches of the Yangtze River,the obtained experimental research results is applicable to the typical gravel sand wave of the Doulizi,Pangxieqi and obstruct in the upper reaches of the Yangtze River.(3)The influence of large-scale gravel sand on the waterway is analyzed by using the measured data of typical navigation hindering reach with gravel sand-wave.It is found that the gravel sand-wave in the Pangxieqi reach and in the middle and lower part of the ShaojibeiLianjiacao reach caused the insufficient width and depth of waterway,which obstructs the implementation of training program and has exerted a great impact on the waterway.The gravel sand-wave in Doulizi reach and near Shaojibei-Chechuancao reach may affect the stability of the downstream waterway,but the current impact is quite small on the analysis.