The pylon foundation of No.3 main tower of Xinbaishatuo Extra Large Bridge across Yan-gtze River was constructed by double-wall steel cased cofferdam.In order to meet the structural safety of double-wall steel cased cofferdam in each stage of construction,modeling calculation and analysis were performed respectively to each construction condition in each stage of construction,such as cof-ferdam assembly,bottom seal,capped slab and tower seat,etc.,so as to ensure safe and reliable structure as well as smooth proceeding of each process.Technique of synchronously constructing bored pile and cofferdam is adopted in construction,the objective of quick construction,safety,good quality and cost saving was reached,the safety of double-wall steel cased cofferdam to tide over flood season was ensured,and solid foundation was laid for the construction time limit objective of the whole bridge.%新白沙沱长江特大桥3号主塔墩基础采用双壁钢套箱围堰施工。为满足双壁钢套箱围堰在施工各阶段的结构安全，分别对围堰拼装、封底、承台及塔座施工等各阶段的施工工况进行建模计算分析，以确保结构安全可靠，各工序顺利进行。施工中采用钻孔桩与围堰同步施工技术，达到了快速施工、安全优质、节约成本的目标，确保了双壁钢套箱围堰的渡洪安全，为全桥的工期目标打下了基础。
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