| Channel maintenance dredging is one of the measures to achieve the goal of waterway navigation.After the channel dredging is maintained,the quasi-dynamic balance of the original local water and sediment-riverbed is destroyed due to the change of the boundary conditions such as local boundaries and water and sediment transport.The estuary and tidal reach are affected by the hydrodynamic force of the tidal current,and the conditions of water and sediment transport are complex.At the same time,the tidal flat of the riverbed is adjusted frequently.The relationship between siltation of the waterway and each factor is not yet clear.Therefore,it is necessary to carry out the research on the relationship between influencing factors of tidal siltation in tidal reach and the identification of main controlling factors.In this paper,we take FujiangSha Reach in the lower reaches of the Yangtze River as research object and use the method of combining the measured data analysis and mathematical model calculation,By summarizing the related research results of domestic and international runoff and tidal river silting back silting,combined with the measured hydrological,sediment and dredging maintenance data,the author focused on the relationship between the evolution of the shoal and the conditions of sediment and sediment,At the same time,by means of mathematical model calculation,the influence of single factor variation on the siltation of the navigation channel is studied by setting the combination conditions of different conditions,thus the main influencing factors of siltation in the navigation channel are determined.The main conclusions are as follows:(1)FJS(FuJiangsha)waterway is in the tidal current changes,showing a curved multi-level branching.Since the trend of the boundary position in the activities in the Fubei waterway,the extent of its obstruction is far greater than the Fuzhong and Funan waterway.The results show that the characteristics of back-silting after excavation of Fubei waterway are related to both the change of runoff and hydrodynamic conditions and the deformation degree of Jingjiang beach and SJS(ShuangJiansha)shoal sand body under the action of water flow.When the traffic flow Q>50000m3/s,FJS reach tidal power relatively increases.At this time,Jingjiang side beach began to scour,sediment in Fubei waterway silt,making the degree of impediment further increase;When the days of Q>60000 m3/s becomes longer,the cutting trend of Jingjiang side beach appears,and a large amount of bottom sand enters the design channel,which further increases the deposition amount of Fubei channel shoal and increases tidal power.At this time,whether the increase in the navigation obstruction degree depends on the size of the cuttings and the strength of the sediment transport capacity of the Fubei waterway.(2)The results of the measured data and the mathematical model show that the size of the runoff and the degree of deformation of the edge beach are the main factors influencing the back-silting of the water channel in the Fubei waterway when the water depth and width are not changed.With the increase of runoff and the degree of deformation of the Edge diara,the silt volume increases.And the effect of Edge diara's deformation on the back-silting is higher than that of runoff.At the same time,the implementation of the second-stage remediation project has obvious effect on the adjustment of the fluctuating power of the Fubei waterway,which is effective for reducing the back-silting of the Fubei waterway,In contrast,only one hydrological year of taking trough dredging can barely change the water depth conditions of the channel. |
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