Shanghai TBMs are world's largest.
Two of the world’s largest tunnel slurry borers are starting to drive 9-kilometer-long tunnels under China’s Yangtze River, in Shanghai. They are a key element of the $1.6-billion, 25.5-km Shanghai-Chongming Expressway. The link between Shanghai, Changxing Island and Chongming Island is to be completed in time for the 2010 Shanghai Universal Exposition.
At the Yangtze’s estuary in Shanghai, one record-breaking, 15.43-meter-dia tunnel-boring machine set off from a shaft at Pudong late last year. The second, close on its heels, is also expected to drive 400 m a month through clay, silt and sand.
The 9-km twin tunnels to Changxing Island are part of the Shanghai Yangtze River Tunnel and Bridge highway, which will continue on a 6.25-km-long viaduct across Changxing and a 10.3-km-long bridge to Chongming Island.
New 9-km-long twin tunnels under Yangtze River at Shanghai are biggest example of China’s tunnel-boring blitz.
Shanghai Tunnel Engineering and Rail Transit Design and Research Institute designed the tunnel, supported by Third Harbour Engineering Investigation and Design Institute, the U.K.’s Halcrow Group and New York City-based Parsons Brinckerhoff’s Asia office.
For its $245-million negotiated civil job, contractor Shanghai Tunnel Engineering Co. (STEC) asked France’s Bouygues Travaux Publics SA for technical support. Bouygues joined the consortium this month, taking a 40% role after securing Grade 1 certification from the city. “There are few contractors which have Grade 1,” says Michel Cote, deputy chief executive of the parent company Bouygues Construction SA.
Germany’s Herrenknecht AG won the TBM supply contract nearly two years ago and began delivering the main components, including cutting wheels, to Pudong in January 2006. There, STEC fabricated heavy steelwork elements and assembled the TBMs, completing the first one last April. It was later dismantled and rebuilt at its shaft 6 km away, to start work on the 7.5-km bore last autumn.
Because of high water pressure, replacing cutter tools will not be possible in compressed air. Tools are designed for extraction by workers in free air from behind. To excavate eight cross passages, each up to 65 m under the river, the contractor will freeze the wet soil. “It’s the safest solution compared to grouting,” Cote says.
The 51.5-m-wide twin box girder main bridge includes a 730-m-long cable-stayed navigation span. China Harbour Engineering Corp. Bureau No. 2 is its main contractor. Approach viaducts, by other contractors, have spans of 60 to 105 m in length in composite and precast construction, notes Jin Ping Zhang, Shanghai director for Denmark’s COWI AS. Halcrow and COWI worked on the design with Shanghai Municipal Engineering Design Institute.
Twin tunnels are bored under pressure beneath river.
North of Changxing, construction is well under way on pylon legs of the cable-stayed section of the bridge. “There’s a lot of progress on the approach bridges,” says Henrik Andersen, project manager with COWI.
Another Yangtze crossing is taking shape some 260 km upstream, at Nanjing. The first 14.93-m-dia slurry TBM for the 3.7-km crossing arrived last autumn and is now at work. Herrenknecht is fabricating the second.
At Wuhan, some 900 km upstream from Shanghai, work began in late 2004 on the Yangtze’s first tunnel. France’s NFM Technologies SA delivered the first 11.38-m-dia slurry TBM last summer for the 2.7-km bored section and the second by year’s end. Boring has begun and a mile of cut-and-cover work is well along, says Alfred Schulter, general manager of Austria’s D2 Consult, the contractor’s technical adviser.
Last year, Herrenknecht alone had supplied nearly 40 full-face TBMs to China. With other suppliers, the total is probably more than 50, estimates an offical with the manufacturer.