U.S. Water News Online
NEW YORK -- One of the world's largest tunnel boring machines is being used to dig five miles of a 16-mile tunnel for water supply that is part of the most expensive public works project in the history of New York City.
Starting at the city of Maspeth, the machine is carving a 38-foot diameter hole through Queens bedrock, 680 feet below the surface. The tunnel will run through Queens to a shaft in Jackson Heights, then turn west to link with a tunnel near Roosevelt Island. Another tunnel currently under construction will serve Brooklyn, linking up with the Queens tunnel in Maspeth. The tunnel will be 750 feet deep by the time it is completed sometime in 1999.
Atlas Capco Robbins, the company which provided similar machines to build the Eurotunnel under the English Channel, custom built the tunnel boring machine for the construction of the Queens Water Tunnel, a $175 million segment of a $1 billion, four-borough tunnel project.
The tunnel is designed to improve water distribution to a major section of the city that currently uses some 200 million cubic feet of water per day. It will also allow inspection and repair of two other water tunnels that have served New York City since 1917 and 1936.
A joint venture of the companies Grow Tunneling, The Perini Corp., and Skanska purchased the machine for more than $12 million and have been contracted to build the tunnel.
According to project engineers, use of the tunnel boring machine (TBM) is safer and less costly than blasting -- the traditional technique. The TBM will carve out a smooth tunnel, while blasting creates a rough, jagged tunnel wall. As the water tunnel will be lined with concrete, much less concrete is needed to line a smooth bored tunnel than a rough, jagged one, according to the engineers.
The 580-ton TBM has a diameter of 23 feet and incorporates the latest main-bearing and cutter technologies to achieve peak performance in hard, abrasive rock. Its main-beam design enables it to sustain heavy loads. It also features a large, three-axis main bearing to sustain high thrust loads. The machine is the strongest of its size that Atlas Capco has ever built.
According to project engineers, use of the tunnel boring machine (TBM) is safer and less costly than blasting -- the traditional technique. The TBM will carve out a smooth tunnel, while blasting creates a rough, jagged tunnel wall. As the water tunnel will be lined with concrete, much less concrete is needed to line a smooth bored tunnel than a rough, jagged one, according to the engineers.
The 580-ton TBM has a diameter of 23 feet and incorporates the latest main-bearing and cutter technologies to achieve peak performance in hard, abrasive rock. Its main-beam design enables it to sustain heavy loads. It also features a large, three-axis main bearing to sustain high thrust loads. The machine is the strongest of its size that Atlas Capco has ever built.
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