A Daewoo Engineering and Construction led contractor consortium has successfully placed the first 45,000 tonnes by 180m long element of South Korea’s first ever immersed tunnel. Halcrow working in joint venture with Tunnel Engineering Consultants of the Netherlands is technical consultant to the main contractor.
The 8.2km long $5.8 billion Busan - Geoje Fixed Link Project includes a 3.2km undersea roadway tunnel that goes far beyond today’s common practice within concrete immersed tunnel technology. Key vital statistics:
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the world’s deepest immersed roadway tunnel at 48m below mean water level and the world’s second longest immersed concrete tunnel |
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the site is exposed to severe open sea marine conditions from the Pacific Ocean
weak subsoil has required extensive soil improvement works |
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the tunnel is above the sea bed at both ends of the alignment |
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to accommodate swell wave conditions the immersion equipment is the largest ever used |
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immersion works have to be in a short weather window out-with the typhoon season |
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provision for seismic loading is included in the design giving special construction challenges |
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double watertight seals are provided at segment joints for the first time |
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two wider elements with climbing lanes will be used at one end, each weighing 48,000 tonnes |
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pre-cast concrete blocks up to 75 tonnes each protect the elements and artificial island entrances |
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the project is a public private partnership with 72% private and 28% government funding and a 40 year concession period |
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placing of element two is planned for early March 08 |
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the link is scheduled to open to traffic before the end of 2010. |
Each of the 18 elements consist of eight, 22.5m long concrete segments of cross section 26.46m wide by 9.97m high, with two dual carriageway roadway bores and a central gallery. Each segment is cast in full cross section and four elements are built at a time in a purpose built dry dock facility. After storing and fitting out at a temporary mooring area, the elements are towed 35km to the alignment and immersed by specialist sub-contractor Mergor Underwater
The permanent works design is by a joint venture of COWI of Denmark and Daewoo Engineering.
