Research On The Influence Of Sand Mining On The Waterway In Wumingzhou Of The Lancang River And Its Remedial Measures

The Lancang River-Mekong River is an international river known as the "Oriental Danube" that connects the six-nation free trade zone.The construction of the 244 boundary marker on the Lancang River to the Grade IV waterway of Lincang Port is of great significance to my country’s development.From April 2016 to March2019,the beach section of the Wuming Chau of the Lancang River was drastically excavated sand,and the topography of the channel section changed dramatically.The sand mining range exceeded 1.2km,the general mining depth exceeded 5m,and the maximum mining depth was as high as 15 m.It not only reduces the flow velocity of the Wumingzhou beach section,and makes the stability of the originally wide and shallow channel worrying;it also increases the flow velocity of the upstream bayonet section,worsens the navigation conditions at the bayonet,and makes it difficult for ships in the narrow section to move up.Therefore,this paper collects the Wumingzhou beach section data and adopts a two-dimensional flow mathematical model calculation method to analyze the impact of sand mining on the channel conditions of the Wumingzhou beach section,and proposes corresponding remediation measures.Through multi-plan optimization research,scientific and reasonable remediation is proposed Program.The research content and results of this article are as follows:(1)Analysis of hydrological characteristics and riverbed changes in Wumingzhou of the Lanjiang River.Collect and analyze the hydrological and sediment data of the Wumingzhou beach section of the Yangtze River,compare the topographic maps before and after sand mining,and analyze the changes in the beach section of the river bed.It is found that sand mining has changed the entire topography of the Wumingzhou beach.The entire beach recedes and digs deeper,the upstream spout has advanced and raised,and weak siltation occurs in the navigable channel.(2)The impact of sand mining on navigation conditions.The sand mining caused a significant drop in the flow rate of the navigation channel in the Wumingzhou beach section,and the main flow of the beach section shifted to the sand pit,which reduced the scouring capacity of the navigation channel and the stability of the navigation channel.In addition,the flow velocity and gradient increase significantly in the bayonet section of the protruding mouth,which increases the difficulty of the ship ascending.(3)The remediation effect of the original recommended plan is reduced.The research on the remediation effect of the recommended scheme of the original remediation project before sand mining shows that under the terrain after sand mining,the remediation effect of the original recommended scheme is significantly lower than before sand mining.The water beam and backwater capacity is limited,and it is difficult to increase the flow velocity of the shallow channel.Maintain the stability of navigation depth.After optimization and improvement,the improvement effect of the original recommended plan is limited,and the stability of the navigation channel is low.(4)Based on the topography after sand mining,research on the multi-thinking rectification measures of Wumingzhou beach section.(1)On the basis of analyzing and understanding the riverbed change analysis and flow characteristics of the Wumingzhou beach section,the conventional method of damming and blocking water jets is adopted to increase the water level and flow velocity of the Wumingzhou beach section to ensure the stability of the navigation channel;Improve the droop velocity at the protruding mouth bayonet,making it difficult to go to the beach in the narrow section.(2)Based on the shape of the new river course after sand mining,new ideas for the regulation of the new navigable channel are proposed.The optimization study of the scheme shows that the excavation of the protruding nozzle and above the new channel section avoids the section with poor beaching conditions at the protruding nozzle of the original channel,thereby improving the navigation conditions of the ship.The new channel not only has better navigation conditions,but also adopts certain renovation engineering measures.The scour capacity of the new channel has been significantly improved,and the channel can remain stable all year round.