Construction Techniques for Double-Walled Steel Box Cofferdams of Pylon Piers of Main Navigation Channel Bridge Carrying a Section of Xinglian Road Corridor over Xiangjiang River
The main navigation channel bridge carrying a section of Xinglian Road Corridor over the Xiangjiang River is a hybrid girder cable-stayed bridge with a main span of 380 m and two side spans of 165 m.The stay cables are arranged in double cable planes.The two pylon piers are supported on dumb-bell shaped pile caps that measure 62.5 m by 22.6 m,7.0 m in height,the tie between the two bells is 11.4 m wide.The top and bottom of the pile cap of main pier No.51 are measured at elevations of+18.0 m and+11.0 m,respectively,the average elevation of riverbed is at+19.0 m and the average water level is at+29.8 m.The pile caps were constructed with the aid of double-walled steel box cofferdams,and the cofferdam of the pylon pier No.5 measures 66.3 m by 26.4 m,24 m in height,featuring the 1.8 m-thick walls,three layers of inner supports and 3.0 m-thick tremie seal.The steel cofferdam suitable for 18.8 m head of water was divided vertically into three lifts and transversely into 20 pieces to achieve a modularized construction,the base lift was manufactured integrally with the steel casings,hoisted by two barge-mounted cranes each with a lifting capacity of 800 t,and delivered to the bridge site by three tugboats.Afterwards,the steel cofferdam and steel casings were elongated in water.Aided by the horizontal positioning system,the steel cofferdam was precisely positioned and landed onto the riverbed,and the pouring of tremie seal and in-fill concrete for the cofferdam cells ensued.No leakage was observed during the construction,indicating the sound quality of the steel cofferdams.
cable-stayed bridgedouble-walled steel box cofferdammodularizationmanufacture of steel cofferdam with steel casingsintegral hoistingin-water elongationconstruction technique
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