Extra large body of bridge bears the whole main bearing foundation of structure of bridge, service life and security of the whole bridge of back cover quality relation of the foundation pit.

That steel hook box cofferdam is that provision design of the hinders water structure for slab foundation construction,whose effect is by the side and the back cover concrete on bottom board or bottom board of the steel hook box cofferdam surrounding water to provide the anhydrous trunk body work environment for slab foundation construction.

With reference to the design and construction of steel boxed cofferdam used at mid-river shoal for the Shengmi Bridge in Nanchang, this paper presents the design process of the single-wall, bottomless huge steel boxed cofferdam, and analyzes in details the construction difficulties of changing of the guiding trusses, internal bracings, sinking and bottom sealing of the cofferdam.

The design and construction technology for rubble grouting concrete of the open caisson wall and of the bottom sealing at the anti impact island of the auxiliary shipping channel of Humen Bridge were introduced,and the economic benefits of adopting the grouting concrete were analyzed in this paper.

In this paper,the construction techniques for the bottom sealing are dealt with.

Combined with practical engineering of sinking well in underground drainage pumping station in Xinlan road,Taiyuan city,the author introduces its hydro-geological conditions,illustrates structural design elements of sinking well and attentions in the design,and analyzes relevant problems in correcting sinking deviation and subsealing construction,which to offer a reference for similar projects.

Construction practice proves that clip insert plate may effectively save the volume of blasting under water, reduce the leakage of floor sealing concrete, and accelerate the construction of foundation in water.