Following the news in April, (T&TI, April, p6), that a MHI-Duro Felguera TBM has equalled and joined Herrenknecht’s world record breaking mammoth 15.2m diameter machine on Madrid’s M-30 south bypass project, Herrenknecht has responded with news in May of the assembly of its 15.43m diameter machine in China for a crossing of the Yangtze river.
Herrenknecht said its mixshield TBM was handed over to the Chinese client Shanghai Changjiang Tunnel & Bridge Construction Co Ltd, at the end of April. It was assembled at the Shanghai Wuhaogou (Pudong) facility of Herrenknecht’s Chinese partner, Shanghai Tunnel Engineering Co Ltd (STEC), in only four months.
This slurry shield is the first of two 15.43m diameter TBMs that Herrenknecht is due to supply to the region. From the beginning of September, the first TBM is due to start a 7.2km long tunnel under the Yangtze at depths of up to 65m below the surface towards the river island of Chagjiang. Water pressures of up to 6.5 bar are expected along the alignment. Once complete, the tunnel will accommodate a three-lane highway to connect the island to the arterial road system. It is due to open in 2010 in time for the city’s hosting of the World Expo.
The second TBM will be used to build a broadly parallel tunnel that will also accommodate a three-lane highway as part of the Changjiang Under River Tunnel Project. This sister machine is currently being assembled at the STEC facility.
Herrenknecht was awarded the contract for the supply of the two mixshields 13 months ago in spring last year. As well as being a first for the manufacture of two machines with this excavation diameter, it also marks the first direct order of Herrenknecht’s “most advanced tunnelling technology” and is considered to be a strategically important contract by the manufacturer.
T&TI was told that the water pressures of up to 6.5 bar can only be mastered safely using the mixshield approach. To allow the crews to change tools at the cutting wheel in such conditions without compromising safety, the set-up has been designed so the six cutting wheel arms are accessible from within the shield under atmospheric pressure, thus reducing the requirement for diving operations.
The first TBM is now being dismantled for transport to the construction site 6km away. It is due to get underway from its 26m deep launch shaft on 8 September. The second TBM is scheduled to be launched three months later on 8 December. The two tunnels will be driven with a centreline separation of 23m, which equates to 9.57m between the excavation profiles. Along the drive, each TBM will install 7,500 segmental lining rings. Each ring consists of 11 segments that weigh up 16t each. The first breakthrough to the reception shaft on Changxing island is programmed for the end of 2008.
The scheme also includes the construction of a bridge between Changxing and the island of Chongming. Total investment in the scheme is approximately US$1.5bn. Herrenknecht said: “This mega project in China is of enormous strategic importance to Herrenknecht. It will send an important signal in Asia as a reference project in large-scale mechanised tunnel construction.”
