Study On The Branching Stream Shoal Of Dark-spotted In The Upper Yangtze River Of San Yanzao

The Sanyanzao beach section is located in the Baisha waterway from the Yibin to Chongqing section of the Yangtze River,and it is a shallow shoal that is divided into submerged moraine.There is a dark moraine in the beach section of the river.The river channel is divided into two grooves on the left and right.Although there is a pier in Baisha Town in the right groove,the channel is curved.Except for the passenger liner,it is not navigable during the dry season.The left slot is relatively straight,and it is the main channel of dry water,but the depth of dry water often does not meet the depth of the flight and is shallow and obstructs navigation.The Sanyanzao beach is a typical submarine shoal shoal.It is of great significance to study the characteristics of the flow,the causes of the obstruction,the evolution of the river bed and the regulation methods for improving the channel level of the beach section,developing the navigation of the Yangtze River and studying the regulation methods of similar beach risks.In this paper,through the analysis of collected data and the use of two-dimensional numerical simulation and other methods,the law of river bed evolution,the causes and mechanisms of beach danger,the characteristics of obstruction of navigation and the improvement measures are analyzed.The research content and research results of this article mainly include the following aspects:(1)Analysis of riverbed evolution of The Sanyanzao beach section in the upper reaches of the Yangtze River : Collect the topographical geology,hydrology and sediment data in the past years,comprehensively analyze the flow conditions such as incoming water and sediment,topographic and geological boundary conditions and beach depth,and systematically carry out river bed evolution analysis.The shoreline of the Sanyanzao beach section is fixed.The vertical and horizontal positions of the trough and The Sanyanzao beach section are stable,the shape of the cross section remains basically unchanged,and the overall erosion and siltation change is relatively small.(2)Analysis of the flow characteristics and causes of shoal hazards in the shallow shoal of The Sanyanzao beach section: The two-dimensional flow mathematical model is used to calculate the multi-level discharge of the study section,and the flow conditions and characteristics of the beach danger are analyzed in detail.It is pointed out that the main reason for the shallow water obstruction of the Sanyanzao beach section is due to the water blocking effect of the Donghaituo narrow section and the sow moraine river continent,so that the beach section is smooth and the sand transport capacity is relatively weak.The submarine mooring,and the main channel is located on the convex bank of the main sand conveying belt,When the water flows into the bend,it is subjected to the centrifugal force directed to the concave bank.The water surface of the concave bank rises,and the water surface of the convex bank drops;the flow velocity of the flood is evenly distributed,and it is difficult to concentrate the current to wash the channel.The shoal belongs to submerged mooring shoal and also has the characteristics of Xiakou Shoal.(3)Research on the optimization of The Sanyanzao beach treatment plan:Based on the analysis of the riverbed evolution in The Sanyanzao beach section and the understanding of the current flow characteristics before the project,three remediation ideas were proposed,namely,constraint water sand flushing,plug support,and the opening of new trenches Program.(1)Through the idea of harnessing sand for sand flushing,build a comb dam in Qianqi moraine,narrow the cross section of the main channel,increase the flow velocity,increase the sand carrying capacity of the current,reduce the siltation of the channel,keep the channel depth stable,and optimize based on The better plan for constraint water sand flushing.(2)Through the plug-and-branch rectification idea,build a submarine dam in the curved channel(right channel)to increase the diversion ratio of the straight channel(left channel),and then increase the flow rate of the straight channel to enhance the sand transport capacity to achieve a stable main channel Rehabilitation requirements of Hang Seng.The mathematical model is used to optimize the parameters of various combinations of dam body,and the reasonable and feasible height and length of the submerged dam are determined.The results show that the construction of a submerged dam in a curved channel has no significant change in the flow characteristics of the straight channel,and the improvement effect is poor.(3)Through the development of the new channel,the right curved channel is selected as the main channel,and the shallow area between the upper and lower deep channels is dredged to avoid the disadvantages of unstable channel depth and insufficient water depth in the left channel,and make full use of it The right slot with richer navigation depth can achieve the purpose of remediation.The results show that the flow velocity in the shallow area of the new channel is greater than that in the upstream richer area,and the degree of sedimentation in the channel is reduced compared to the upstream.At the same time,the river channel erosion rate of the new channel is greater than the original design channel,and the degree of sedimentation It is shallower,and the crossflow of the new channel is weaker,and the water surface is smoother,which can be used as a comparison scheme.