Abstract: Fuzhou Daoqingzhou Crossing is located at the estuary of the Minjiang River,and is affected by half day tides,resulting in significant changes in the tidal range of the river section,which requires high requirements for the design and construction of cofferdams. The cap of S18 # bridge pier is constructed using double-wall steel suspended box. Taking this bridge as an example,the structural design and construction technical points of the double-wall steel suspended box cofferdam under the influence of high tide difference in estuarine environment are explained. The entire construction process of the cofferdam meets the requirements of structural anti-floating and anti-sinking,and provides a reference method for the design and construction of steel suspended boxes in similar water environments.

Key words: estuary, double-wall steel suspended box, internal support, strengthened truss, system conversion