Both of Herrenknecht’s 15.4m diameter slurry TBMs were in the ground mid-January driving twin bores under the Yangtze river, China.
A spokeswoman said the second of the TBMs – which the German manufacturer claims are the biggest of their class – started excavation on 17 January. The first TBM began its 7.17km drive between Pudong and Chongming Island on 23 September last year.
The four-year tunnelling project on the Shanghai Changjiang Under River Tunnel project will have each tube carrying three lanes of traffic above a safety passage and rescue lane (T&TI, October 2006, p8).
Geological conditions facing contractor Shanghai Changjiang Tunnel & Bridge Construction Development Co along the tunnel alignment broadly consists of sand, clay and rubble. The TBMs are to drive 65m below ground at their deepest point and the maximum groundwater level above the tunnel axis is estimated to reach 47m.
Elsewhere, last November also saw work commence on a 2.1km twin tunnel being built in Henan province. Joint venture contractors, China Railway 15th Construction Bureau and China Railway Tunnel Group, hope to finish the tunnel late this year.
The project is only a quarter the length, however, of the road tunnel to be built on a 134km toll highway between Wudu and Guangzigou in Gansu province. Along with a host of short bores on the project, the tunnelling works will total more than 37km and work is scheduled to start in 2008.
