The TBM supply contract is due to be tendered this month for the 5,813m long Nanjing Yangtze river crossing in China that incorporates twin 13.3m i.d. highway tunnels 3,710m long.

Danish engineers Cowi have been assisting the client, Nanjing Yangtze River Tunnel Project, with the preparation of the TBM specification for the scheme. Cowi’s project manager, Søren Degn Eskesen, told T&TI that the civils works contract for the US$362M build-operate-transfer (BOT) scheme was also due to be sent out to tender in September. He said that TBM delivery was required for early 2007, with the tunnel due to open as early as 2009.

T&TI has learnt that two slurry machines are to be used on the project, with an external diameter of 14.5m. With an alignment that gives just 10m clearance to the riverbed, the TBMs will have to bore through soft river deposits of clay, silt and sand. In late August, Eskesen told T&TI that site investigations from barges in the river were presently ongoing.

The project also includes a 610m long bridge and an island between the bridge and the tunnels. Each tunnel will contain three lanes, 2 x 3.5m wide and 1 x 3.75m wide, to accommodate traffic at speeds up to 80km/h. The tunnels will be linked by 12 cross passages. Once completed, the tunnel will link the northern and southern districts of Nanjing.

Cowi has identified China as “a large market, and the need for tunnels is expanding vigorously, partly due to large investments in the country’s infrastructure”. Also involved in the project as subconsultants are Ways & Freytag.