The main bridge of Yingwuzhou Changjiang River Bridge in Wuhan is a three‐tower steel and concrete composite girder suspension bridge with span arrangement (200+ 850+850+200) m .The foundation of the intermediate tower pier (Pier No .2) of the bridge is composed of 39 nos .of diameter 2 .8 m bored piles .The pile cap is in the round‐end rectangular shape that is 70 m long ,34 m wide and 6 .5 m high and the pile cap is embedded in the riverbed overburden .The foundation was constructed by the general scheme of double‐wall steel boxed cofferdam and of con‐structing the cofferdam first and the working platform late .Before the cofferdam was floated and positioned ,the soft mattress was laid out on the riverbed to serve as the active protection in order to lessen the scouring of the riverbed due to the construction of the foundation .The first lift of the cofferdam was manufactured on bank and was launched to the river by the air bag method .The lift of the cofferdam was turned first ,then launched to the river in a straight line and positioned by the system of "front and rear positioning barges+heavy anchors".By pumping water into the walls of the cofferdam ,the cofferdam was rapidly landed onto the riverbed .After the cofferdam was sunk down in place to the designed elevation by dredging ,the working platform was set up and the con‐struction of the bored piles started .The base of the cofferdam was cleared off ,sealed by concreting and the pile cap was finally constructed in two layers according to the workmanship of massive concrete .%武汉鹦鹉洲长江大桥主桥为（200＋850＋850＋200） m三塔钢－混结合梁悬索桥，该桥中塔（2号）墩基础采用39根直径2．8m钻孔灌注桩，承台为圆端矩形，长70m、宽34m、高6．5 m，埋置于河床覆盖层中。中塔墩基础采用双壁钢套箱围堰和“先围堰、后平台”的总体施工方案。在围堰浮运定位前，先在河床面铺设软体排进行主动防护，以减少基础施工对河床的冲刷；底节围堰在岸上制造，采用气囊法下河，先转向后直线下水，利用“前后定位船＋重锚”系统定位，通过向井壁注水快速着床，围堰吸泥下沉到位后，搭建施工平台进行钻孔桩施工；最后进行围堰清基、封底，分2层按大体积混凝土工艺进行承台施工。
展开▼
