Nanjing Mixshield breakthrough!

The mighty Yangtze in China is once again conquered by modern TBM technology. On May 20 and August 22 respectively, two Herrenknecht Mixshield giants, of 14.93m diameter each, crossed beneath the Yangtze to reach their target in Nanjing. These twin 3km long highway tunnels join the successful completion last year of the two 15.43m diameter Herrenknecht Mixshields that completed the 7.47 long Changjiang highway tunnel tubes under the Yangtze in Shanghai.

After the start of tunnelling in Nanjing in January 2008 (Mixshield S-349) and May 2008 (Mixshield S-350), these two14.93m diameter giants - among the largest TBMs in the world - made their way safely through highly water-bearing gravel and silt layers to the other side. With an overburden of sometimes only 30m to the river bed and water pressures of up to 7.5 bar to be supported, supreme reliability at the face was required.

The Herrenknecht S-350 achieved breakthrough at the target shaft on the left-hand route on May 20, 2009, and S-349 TBM reached its final destination on August 22, 2009.

Three-lane tunnel interior

The two companies managing the project, the Nanjing Changjiang Tunnel Project Co. Ltd, and China Railway 14th Bureau Group Co. Ltd, can be proud of their achievement. The advance of up to 32m of completed tunnel per day constitutes a top performance for tunnelling machines of this scale. The best weekly performance was achieved at the end of July 2009 with 146m of newly produced tunnel built in one week. The Herrenknecht experts involved in the project can also be proud of what they achieved. Alois Eisendle, Herrenknecht AG's top on-site representative on the Nanjing project, received a particular honor for his work. He was awarded the May Honorary Labor Medal by the Federation of Trade Unions of Jiangsu Province. Nanjing is the central city of Jiangsu Province and is an important transportation hub on the axis leading inland from Shanghai. The two three-lane road tunnels of 2,985m and 2,990m, under the River Yangtze will channel rapidly growing highway traffic through the city and ease transportation congestion significantly.

Chinese customers appreciate Herrenknecht as a supplier of tunnelling machines with large dimensions and for particularly demanding missions. The world's two largest Mixshields (S-317 and S-318) successfully completed excavation of the two 15.43m o.d. x 7.47km long Changjiang highway tunnels under the Yangtze in Shanghai last year. The tunnels will be opened to traffic before the end of this year, thus connecting the district of Pudong with the Changxing River Island in time for the city's hosting of Expo 2010. This project set new global standards in mechanized tunnel construction. Excavation of the two tunnels with three traffic lanes each was completed in only 20 months.