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Robbins EPB to Excavate Chengdu's New Metro
The 11 million inhabitants of Chengdu, China, will soon have a reduced commute time thanks to an extensive new metro system. Five lines totaling 78 miles will be constructed using multiple TBMs. Robbins signed a contract with China Railway Construction Corp Ltd. (CRCC) in January 2009 for a 20.5 ft-diameter EPB and Robbins is back-up system onLine 2, Lot supplying a 20.5 ft di18 of the Chengdu Metro. A ameter EPB commissioning ceremony was and backheld in Chengdu on Oct. 14. up system Geology will include a to China matrix of weathered rocks Railway found nowhere else in China, Construcconsisting of highly permetion Corp able pebbles, sand and clay. Ltd. for Subsidence will be intenconstrucsively monitored — crews tion of Line 2, Lotwill utilize probe drilling 18 of the and ground consolidation if Chengdu settlement is detected. Metro. A mixed ground cutterhead, mounted with 17-in. diameter disc cutters and carbide bits, will be utilized to excavate the variable geology. Cobbles averaging from 0.8 to 3.1 in. in diameter are predicted, with diameters of as much as 4.7 in. possible. Muck will be removed using a 31-in. diametershaft-type screw conveyor and battery-operated rolling stock. Assembly of the TBM was completed in a manufacturing facility in Chengdu. The machine was due for launch in the fall, and will bore two 0.8-mile long sections in a suburban area of the city. The tunnel alignment will allow the machine to pass 82 ft below residential buildings, and includes several curves with a minimum 1,300 ft radius.Active articulation will be utilized to prevent ring deformation in curved portions of the tunnel. The Chengdu Metro will open in three stages, with Line 1 operational by 2010. The 16.6-mile long Line 1 will provide service between Honghuayan and Shiji Square stations at speeds of 50 mph. The 31.4-mile long Line 2, for Chengdu Metro LLC, (with 10.9 miles of underground tunnels) will include 26stations between Longquandong and Shiniu areas. Seven lines totaling 170 miles are planned to be in service by 2035, servicing 13.1 million daily passengers.

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TBM: Tunnel Business Magazine

February 2010


Microtunneling RCP with Crossings of NJ Turnpike and CSX Railroads
By Zhenqi Cai and Alberto G. Solanahe Bergen County Utilities Authority (BCUA) was mandated by a New Jersey Department of Environmental Protection consent order to eliminate by 2010 wet weather overflows through a 50-year-old, 60-in. diameter RCP trunk sewer system into surrounding waterways. As a result, BCUA commissioned the design and construction of a new relief sewer installed in parallel to the existing system.


Thisrelief sewer line is part of an overall scheme undertaken by BCUA to provide additional capacity and redundancy for sewage conveyance from its service areas to its wastewater treatment plant (WWTP). It consists of the installation of 5.3 miles of new interceptor pipelines that vary in diameter from 42 in. to 96 in. through one of the most densely industrialized areas in the region.

The projectsite and ground conditions required several different construction techniques, including conventional open-cut, microtunneling and subaqueous installation. The entire project was contracted in three separate packages – two open-cut only contracts and one contract with a combination of microtunneling, subaqueous installation and open-cut. BCUA retained Hatch Mott MacDonald as the engineer for theplanning, design and construction management of the entire project. The construction of the microtunnel (combined with subaqueous construction and open-cut) was awarded to Northeast Remsco Construction.

Ground Characterization
The ground conditions along the microtunnel alignment feature two distinct geological settings, divided by the New Jersey Turnpike (NJTP). To the west of the NJTP there...
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