April 10, 2012, marked a milestone in the construction of the Metro Line 9 in Beijing, when a Cat tunnel boring machine (TBM) made a major breakthrough in a section with very difficult geological conditions. Beijing Metro Line 9 will provide an additional 16.45 km of metro and is planned to be operational by the end of 2012.
The project owner, Beijing MTR Corp., together with the contractor, Beijing Urban Construction Group (BUCG), held a ceremony at the construction site together with managers from Caterpillar Tunneling Canada Corp. (previously known as LOVAT). China’s official CCTV and other general and trade media covered the ceremony.
The construction of Lot 6 of the Beijing Metro Line 9 consists of two parallel tunnels with a total length of 1.2 km each that pass underneath a lake in the western part of the capital. It is believed to be the most difficult section that the alignment has to run through due to the water-rich conglomerate containing big boulders (1.2 to 1.5 m), which are rarely seen in other subway projects in China or anywhere else around the world.
Caterpillar Tunneling Canada worked closely with BUCG and supplied a 6.28-m, 1200-kW earth pressure balance tunnel boring machine specially designed to tackle such tough geological challenges. After 746 days of underground excavation, the contractor aptly nicknamed the TBM Diamond due to the unprecedented long life of the proprietary Caterpillar Tunneling ripper teeth. The system set a new performance benchmark for fracturing boulders in this complex geology.
In addition to the Beijing Metro Line 9 Project, Cat TBMs have delivered outstanding performance in similar metro projects in Guangzhou, Shenzhen and Chongqing in southern China.