SHANGHAI, China, Sept. 19, 2008 -- Two Herrenknecht tunnel boring machines, the largest in the world with a diameter of 15.43 meters, successfully completed their crossing beneath the Yangtze River in Shanghai. On May 28 and September 5, 2008, the two Mixshields met their target shafts precisely on the Yangtze River island Changxiang -- far ahead of schedule. The 7,472 meter long tunnels connecting the Shanghai district of Pudong with Changxiang island have created efficient transport systems in only 20 months.
The Herrenknecht Mixshield S-318, one of the two largest tunnel boring machines (TBM) in the world with a diameter of 15.43 meters, reached its target shaft on the Yangtze river island Changxiang on September 5, 2008. But not only this giant showed a top performance, excavating an almost 7.5 kilometer long tunnel tube in highly water-bearing construction ground in only 20 months. A good three months before, on May 28, 2008, the identical Herrenknecht Mixshield S-317 reached its target shaft with great precision. Using the two high-tech giants from Schwanau, the shell of the two parallel running large diameter tunnels, which are scheduled to be opened for car and subway traffic for the 2010 World Exhibition, could be completed 10 and 12 months ahead of schedule respectively.
At the beginning of September, the red carpet was rolled out for politicians and construction experts when Shanghai's vice mayor, Jun Shen, proudly announced the successful completion of tunneling at the "Shanghai Yangtze Under River Tunnel." Following final completion, both tunnels will accommodate a three-lane road on the upper level and a subway line on the lower level. The completion of tunneling work ahead of schedule provides the ideal conditions to open the tunnel on time for the 2010 World Exhibition in Shanghai.
The performance of the construction site team and the strong performance of the two Herrenknecht Mixshields were the basis for quick and safe tunneling on this superlative project. With an overburden of up to 65 meters, the machines burrowed their way through sand, clay and groundwater with water pressures of up to 6.5 bar. Weekly tunneling performances of up to 142 meters of constructed tunnel were reached, performance per day was up to 26 meters. The teams operating the TBMs directed the 2,300 ton and 125 meter long colossus with highest precision. On a route of 7.5 kilometers, they deviated only 2.7 centimeters from the ideal line. Now, the two tunnels of the "Shanghai Yangtze Under River Tunnel" connect the Shanghai district of Pudong with Changxiang island on the Yangtze river. From 2010 onwards, the combined road and subway tunnels will reduce the traveling time between Shanghai and the Yangtze river island Changxing from 1 hour to 20 minutes and replace the existing ferry connections.
The two breakthroughs at the "Shanghai Yangtze Under River Tunnel" are an important milestone in mechanized tunneling. As reference projects, they demonstrate that the challenges of structural engineering for extremely large tunnel profiles can be mastered with bravura when it comes to construction times, budget and safety using the technical know-how of mechanized tunneling. They constitute an impressive success for both the Changjiang Tunnel & Bridge Construction, Ltd. and the partnership between Shanghai Tunnel Engineering Co., Ltd., Bouygues TP and Herrenknecht, the technology and market leader in mechanized tunneling from Schwanau (Southern Germany).
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