Research On Effect Of Construction Of Yang-Cheng Lake Bridge For Beijing-Shanghai High Speed Railway

Yang-cheng Lake is the the third largest freshwater lake on the Taihu Lake plains, which is one of the important fresh water lakes in Jiangsu province and one of the important reference sources in Suzhou. It charges with the lake's drinking water supply tasks of the Suzhou City, Kunshan City and nearly one million people in towns along the lake. The Beijing-Shanghai high-speed railway is the longest mileage-building, the largest investment and highest standards of high-speed railway since the founding of china. It pass through Beijing, Tianjin, Shanghai, and Hebei, Shandong, Anhui, Jiangsu province. It will reduce 5 hours from Beijing to Shanghai when operating. There are seven sections passing across the Yang-cheng Lake. The total length is 5900m.There are 181 pier-bits in the lake. The DK1226～DK1263 section pass through Yang-cheng Lake water source protection zones. Two construction plans, which are double cofferdam dam construction plan and steel bridge construction plan, are considered. The construction will have influence on the original lake flow. It is necessary to investigate the flow in order to obtain the law of influence, for direct construction.The flow is simulated during construction by Delft-3D software. The simulation is focused on four stages, which are the original two-dimensional flow simulation before construction, the two-dimensional flow simulation during cofferdam construction, the two-dimensional flow simulation during steel trestle and the two-dimensional flow simulation during bridge pier. The comparison of the two-dimensional flow of the original flow and the flow during cofferdam construction, the two-dimensional flow of the original flow and the flow during bridge pier, the two-dimensional flow of the flow during cofferdam construction and flow during bridge pier construction are made. Then, the construction method is decided based on the analysis results.From the simulation we can see that the direction of flow of the whole lake is not changed by cofferdam construction and bridge construction. cofferdam construction and bridge construction have little influence on the velocity of flow of the entrance and southwest area. cofferdam construction and bridge construction reduce the the velocity of flow of the narrow throat of lake,the vicinity fo the construction and Pacific Wanli drinking water source protection area. It is mainly because the construction produce water barrier,reducing velocity.In some areas,The reduced amount of velocity during cofferdam construction is more than which during bridge construction.It is mainly because the cofferdam construction produce the overall barrier near by the construction.As to bridge construction,it is just piers in water producding a little barrier.The barrier area of cofferdam construction is bigger,so the area of flow reduction of the lake is bigger. Overall, cofferdam construction and bridge construction will have certain influence on flow.The influence produced by bridge construction is less.The influence during cofferdam construction and bridge construction is temporary,which will end after construction.