公安长江公铁两用特大桥3号墩双壁钢吊箱围堰设计

Design of No.3 Pier Double-walled Steel Boxed Cofferdam of Gong'an Yangtze River Rail-cum-road Super-long Bridge

公安长江公铁两用特大桥主桥为(98+182+518+182+98)m的双塔双索面钢桁梁斜拉桥,其3#桥塔墩采用变直径钻孔摩擦桩基础。3#墩基础施工采用双壁钢吊箱围堰方案。围堰为圆端形结构,尺寸为68.2 m(长)×40.0 m(宽)×23.5 m(高),分2节,底节高18.0 m,顶节为单壁,双壁厚2.0 m。该围堰的设计充分考虑了其建造、运输和运营阶段的主要工况,并结合现场实时反馈的情况对围堰结构进行结构修改和检算。计算结果和工程实践均表明围堰结构合理、可靠。

The main bridge of Gong＇an Yangtze river rail-cum-road super-long bridge is a double-pylon and doublecable plane steel truss girder cable-stayed bridge with span arrangement of（98 ＋ 182 ＋518 ＋ 182 ＋98） m.The foundation for the No.3 pylon pier is the one of frictional bored piles with variable diameters and constructed by the scheme of double-wall steel boxed cofferdam.The cofferdam is a round-end structure with a size of 68.2 m long,40 m wide and 23.5 m high,which is divided into two lifts with the bottom lift being 18.0 m high and the top lift being a single wall,the double-wall thickness is 2.0 m.On the basis of fully considering the main working condition of the cofferdam within its construction transportation and operation stages,combining the situation of real-time feedback,the cofferdam structure was designed and checked.The calculation and engineering practice prove that the cofferdam structure is reasonable and reliable.