新白沙沱长江特大桥3号墩双壁钢套箱围堰施工技术

Construction Technology of Double-wall Steel Boxed Cofferdam of the No.3 Pier for New Baishatuo Yangtze River Bridge

渝黔铁路新白沙沱长江特大桥主塔墩3号墩位于主河槽通航航道上，水深15～20m，河床地形条件复杂，部分为水下爆破区域，存在卵石覆盖层、倾斜光板岩，突石等多种情况；基础施工采取先平台后围堰的方案，且钻孔与围堰同步双层作业。3号墩桩基础为36根直径3？2m的钻孔桩，承台施工采用双壁钢套箱围堰方案。对该套箱围堰的组拼、下沉、定位、堵漏、抛填等施工工序中应用的工艺、技术措施进行了分析总结。

The No. 3 main tower pier of New Baishatuo Yangtze River Bridge in Chongqing-Guiyang Railway is positioned on the navigation channel of the main river channel. The depth of water is about 15 to 20 m, the bed topography condition is complicated that a part of the bed topography is underwater blasting area, and several situations of covered pebble bed, inclined bare rock, raised rocks are existed. The foundation construction adopts the scheme of starting with the construction of the platform and then the cofferdam, and drilling and cofferdam are operated synchronously on two decks. The pile foundation of the No. 3 pier is 36 drilled piles with the diameter of 3？2 m, and the cushion cap construction adopts the double-walled steel boxed cofferdam scheme. The technologies and technical measures applied to the construction procedures of assembling, sinking, positioning, leaking stoppage, dumping filling are analyzed and summarized.