EPB beats advance of 11 other TBMs in Chengdu
EPB beats advance of 11 other TBMs in Chengdu May 2010
Desiree Willis, Technical Writer, The Robbins Company
A total 457.5m (1,500ft) advanced in the month of March 2010 is claimed by Robbins as a city-wide excavation record on the Chengdu Metro project in China.

A 457.5m/month speedy EPBM

There are 12 TBMs working currently on the city's Metro, and the 6.26m (20.5ft) diameter Robbins EPBM progressed faster than any of the 11 others in March, recording rates of up to 24m (79ft)/day. The machine began excavation of Line 2, Lot 18 of the project in January 2010 for the China Railway Construction Corp, Ltd. (CRCC).
By May, the machine had excavated about 1,000m (3,280ft) of the 2.7km long tunnel, to be bored in two sections. Cutter wear was minimal, with no cutters changed since the start of boring. "These achievements are due to the strong support of field service during assembly, commissioning, maintenance, and excavation," wrote Mr. Li Quanshe of CRCC in a letter to Robbins.
The Robbins machine was designed to excavate a matrix of alluvial geology found nowhere else in China.
A mixed ground cutterhead, mounted with 17-inch diameter disc cutters and carbide bits, was manufactured specifically to effectively excavate the highly permeable pebbles, sand, and clay geology. A foam injection system stabilizes running ground, with each cubic meter of foam mixture able to stabilize about 40 rings of progress.

The 6.26m diameter Robbins EPB was launched in January 2010

Subsidence is being intensively monitored and crews are trained to utilize probe drilling and ground consolidation to counter any settlement detected.
China's Chengdu Metro will open in three stages. The 26.7km Line 1, providing service between Honghuayan and Shiji Square stations, will become operational in 2010. The 50.6km Line 2, by Chengdu Metro LLC, has 26 stations between Longquandong and Shiniu areas and includes 17.6km underground in bored running tunnels. Seven lines totaling 27 km (170 miles) are planned to be operational by 2035 to service 13.1 million passengers daily.
Robbins EPBM to China's new Chengdu Metro - TunnelTalk, Oct 2009

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