沌口长江公路大桥主墩钢围堰施工技术

Construction Technology of Steel Cofferdam for Main Pier of Highway Bridge over Zhuankou Yangtze River

沌口长江公路大桥主桥为钢箱梁斜拉桥,两桥塔主墩均位于水中,设整体式承台,承台规模为26m×52.2m×6m。每个承台设置32根Φ3.0m钻孔灌注桩,桩基及承台采用围堰法施工。大型钢围堰在长江干流黄金航道内下沉采用了单定位船定位系统,该系统操作简便,施工水域占用少,降低了对通航的影响,最终实现了钢围堰在高速水流作用下平面定位精度在15mm以内,垂直度在1/500以内。同时考虑到浅覆盖层围堰着床受冲刷作用影响明显,通过物理模型试验,确定了冲刷防护体总体布置,保证了围堰终沉稳定性。

The main bridge of the highway bridge over Zhuankou Yangtze River is a cable-stayed bridge with steel box girder.The main piers of two towers are located in water,and integral-type cushion caps are set up,with size of 26m×52.2m×6m.Thirty-twoΦ3.0m cast-in-place bored piles are installed in each cap,and the pile foundation and cushion cap are constructed by cofferdam method.The positioning system of single positioning ship is adopted for the sinking of large steel cofferdam in the golden channel of stem stream of Yangtze River.The system is simple to operate,occupies less construction water area and minimizes the impact on navigation.Finally,the plane positioning accuracy of the steel cofferdam under the action of high-velocity flow is within 15 mm,and the verticality is within 1/500.At the same time,considering that the impact of scouring on the cofferdam of shallow covering layer is obvious,the overall layout of protection body scouring is determined by physical model test,so as to ensure the terminal settling stability of cofferdam.