The foundation construction in deep water is one of the important symbols to measure the level of bridge con-struction.It is not only affected by the water flow and the environment,but also by the geological conditions,construction process and other factors.Dongting Lake Bridge is a three tower,double cable plane,steel box girder and steel truss com-bined girder cable-stayed bridge.It belongs to a part of the railway line from West Inner Mongolia to Central China.The depth of the pier for the No.3 main tower is over 20 meters.Moreover,the environment and the geological condition are complex and changeable.So it is a good choice for deep water foundation to adopt the double wall steel cofferdam.The height of bottom cofferdam section is 19.7 m.Firstly,the steel cofferdam is assembled on shore,and then it is submerged into the water by balloons.The cofferdam is integrally transferred to the right of pier site,and fixed at the right position. After that,it is connected a middle section cofferdam with 4.3 m,suctioning the mud of cofferdam bottom,sinking and putting in place,installing the platform of drilling,pouring concrete underwater to make cofferdam back cover.Bearing platforms are constructed after the completion of bored pile.By measuring and checking the cofferdam after pumping,it is proved that the construction of No.3 main pier adopting the double wall steel cofferdam is accurate and successful.%深水基础施工技术是衡量桥梁施工水平的重要标志之一，其不仅受水流及环境的作用，还会受到地质条件、施工过程等因素影响。蒙西华中铁路洞庭湖大桥为三塔双索面钢箱钢桁结合梁斜拉桥，3＃主塔墩位处水深超过20 m，所处环境及地质条件复杂多变，深水基础采用双壁钢围堰施工。围堰底节高19．7 m，在岸上制造拼装完成后，采用气囊法下河、整体浮运到墩位处，进行抛锚定位、接高4．3 m 中节围堰，吸泥清底、下沉着床到位，安装钻孔平台、水下灌注混凝土进行围堰封底。封底完成后进行钻孔桩施工，钻孔桩施工完毕，抽水后进行承台施工。通过对围堰抽水后的测量检查，证明3＃主墩双壁钢围堰施工定位准确、封底成功。
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