The non‐navigable span bridge of the Hong Kong‐Zhuhai‐Macao Bridge over the shallow water area is a 85‐m span continuous composite girder structure ,the foundations for the bridge are the steel pipe composite pile foundations and the pile caps and piers supported on the foundations are the precast structures .The foundations were constructed by the interlocked doub‐le‐wall steel boxed cofferdams with no internal bracings .A cofferdam is 17 .6 m long ,13 .4 m wide ,23 .2 m high and the thickness of the bulkhead of the cofferdam is 0 .75 m .The cofferdam was designed into a removable structure and in plan ,was divided into 8 segments which were inter‐connected by the combination way of tenon locks and bolts .The cofferdam is mainly made up of three parts of the lateral plates ,horizontal ring plates and vertical partition plates and joints .In accordance with the different force conditions of the cofferdam in the construction process ,4 load cases were considered in the design .The software MIDAS Civil 2006 and ANSYS were used to set up the finite element models for the different load cases and the displacement and stress of the cof‐ferdam and its base sealing structure were analyzed .The results of the analysis indicate that the values of the maximum displacement and stress of the cofferdam and the base sealing concrete structure under the different load cases are all less than those as specified in the codes and can meet the requirements ,proving that the force conditions of the cofferdam in the construction are safe and the cofferdam is structurally rational .%港珠澳大桥浅水区非通航孔桥为跨度85 m的连续组合梁结构，其基础采用钢管复合桩基和预制墩台结构，基础采用无内支撑结构的双壁锁口钢套箱围堰施工。围堰长17．6 m、宽13．4m、高23．2m，壁仓厚0．75m。围堰设计成可拆装式结构，平面分为8块，各分块之间采用榫头式锁口与螺栓组合的方式连接。围堰主要由侧板、水平环板与竖隔板、围堰接缝三部分组成。根据施工过程中围堰受力的不同，分4个工况，采用有限元软件MIDAS Civil 2006及ANSYS建立各工况的有限元模型，分析围堰及封底混凝土结构的位移及应力。结果表明，在各个工况下，围堰及封底混凝土结构的最大位移及应力均小于规范允许值，满足规范要求。表明围堰在施工过程中受力安全、结构合理。
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