English：

Based on the main channel bridge of the Xinglian Road Grand Corridor Project in Changsha,the design and construction key technologies of double,wall steel cofferdam for deep,buried abutments inhard rock were studied. Taking into account factors such as geology, hydrology, and resource allocationat the bridge site, an integrated structure of double,wall steel cofferdam and steel casing was designed,and the overall stress of the double,wall steel cofferdam was analyzed. The overall design,manufacturing, and installation methods of the steel cofferdam and steel casing were proposed. Theconstruction process of vertical sectionalization and overall docking of large,section steel cofferdams onwater was adopted, and a steel cofferdam floating positioning system was developed. A complete set oftechnologies for the integrated manufacturing, docking, and positioning of casing and steel cofferdam wasformed, achieving rapid and precise positioning of the steel cofferdam and steel casing as a whole,reducing the workload of deepwater operations and saving the installation period of the steel casing in thelater stage.