China Railway Tunnel Group last month completed the first drive on the twin bore road tunnel below the Yangtze river at Wuhan, Hubei province, with a 11.38m diameter NFM Technologies’ slurry TBM.
The second, identical TBM is expected to hole through on the parallel drive at the end of February, having started its 2.7km long drive just under a year ago. Then the first TBM had advanced less than 10% of its drive.
Excavation had been expected to be completed about the end of 2007 but the TBMs have been able to perform their drives without the need to change disc cutters or drag bits.
The machines were fitted with bucket and face scrapers from TunnelTec in the first use of its tools in China.
NFM noted that such replacement work could have required hyperbaric operations as 1.7km of each drive was in critical geological conditions with pressures up to 7 bar.
Tunnel boring was through silt and sand with clay and large boulders.
The average daily progress rate achieved by the TBMs in the difficult geological conditions was 15m-20m, said NFM.
In total, each tunnel will be 3.63km long and the twin bore crossing of the Yangtze is part of a new main artery route that will run north-south across the city, which is divided by the Yangtze and Han rivers. The road will be a double carriageway with two lanes each in the tunnels.
Celebrations in Wuhan, China, when the first of twin NFM slurry TBMs holed through after driving below the Yangtze river
