Records Rally for Robbins EPBs in Guangzhou

Aug 17, 2009

Two TBMs achieve Best Project Rates 16 Times Over: After seven months of tunneling and more than 16 project records, two Robbins EPBs are pushing far ahead of schedule.  The 6.3 m (20.5 ft) diameter machines for China's Guangzhou Metro are more than a month early and on track for breakthroughs in August and October 2009, respectively.

Records include a best month of 377 m (1,235 ft)-higher than any of the 16 TBMs that have worked on the Guang-Fo Metro Project.  "The excavation speed of these machines has been praised by the project owner, Guangzhou Metro Company, many times.  We believe the high rates are a combination of fewer equipment failures and efficient project management," said Mr. Ju Yicheng, Vice Chief Project Engineer for contractor China Communication Construction Corp., 2nd Navigation Engineering Bureau Ltd. (CCCC).
Ground consists of weathered granite, coarse sand, and silt with earth pressures of up to 4 bar.  Four independent foam injection points in the cutterhead are used to consolidate the face and create a smooth flow of muck in the mixed ground conditions.
Active articulation systems have also allowed the machines to make curves down to a 200 m (820 ft) radius with no ring deformation.  This type of articulation allows the front shield to turn independently of the machine's thrust cylinders, applying even pressure to each ring in tight curves.
The Robbins EPBs are boring parallel 2.6 km (1.6 mi) long tunnels for the Guangfo line of the new metro, which will connect the neighboring cities of Guangzhou and Foshan.  The line is part of the Chinese government's Inter-city Rapid Rail Project, which aims to link up nine cities in Guangdong Province by 2015, including Shenzhen and Dongguan.

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