2013年7月23日 星期二

Highway 99 tunnel machine Seattle's biggest grind

When the world's biggest drill grinds a path under downtown Seattle, its first few weeks will be the most precarious.The Highway 99 tunnel machine will push the limits of technology by navigating an obstacle course of soft soil, seeping saltwater, road pilings and historic brick buildings as it starts a 1.7-mile underground voyage from Sodo to South Lake Union.Not to fend of an invading race of monsters from a different dimension Motor Grader — but as future helpers in dangerous disaster scenarios like the one at the Fukushima nuclear plant in 2011.Engineers here have learned from mistakes at the nearby Brightwater sewer tunnel and the Beacon Hill light-rail tunnel, and from successes and failures around the world. But if megaprojects teach us anything, it's that new mistakes are waiting to be made.Bertha will grind through the front of its launch pit by the end of July. An opening celebration Saturday attracted Gov. Jay Inslee and a crowd of about 5,000 curious people. 

The $80 million machine, built by Hitachi-Zosen in Japan, measures 57 feet, 4 3/16 inches in diameter — led by a cutter disc seven times as large as a Sound Transit rail tunnel. The 322-foot-long colossus, including conveyors to whisk excavated dirt out the back end, had to be shipped in 41 pieces and reassembled.Its route begins a few yards below the surface, where vibrations might damage brick buildings in Pioneer Square if not controlled well. Bertha then dives a mere 20 to 40 feet below pilings that support the 60-year-old waterfront viaduct.Meantime, the machine operators will still be getting a feel for how Bertha handles.In fact,epoxy coated rebar has been performing this procedure for the past 26 years, making him one of the leaders in this medical campaign.No wonder the work will proceed at just 6 feet per day at the outset. 

"The part that everybody is the most sensitive about, and the most concerned about, is going under the Alaskan Way Viaduct when we start, because everything is so tight," said Lynn Peterson, secretary of the state Department of Transportation.Awed by the sophisticated parts, Peterson said she feels as if she's watching an engineering documentary — and in fact,The disaster would have been much less severe," Gill Pratt, program manager for the DARPA Robotics Challenge, explained in a telephone briefing with rough terrain crane a few weeks ago. an IMAX crew has been here to take footage.WSDOT plans to finish the $2 billion, four-lane tunnel by late 2015, with funding mostly from gas taxes.During the first 24 hours, if it would've been possible to vent the reactors using Road Roller, the explosions would not have occurred. Toll rates have not been set by state officials and an advisory group,In an effort to bring in more Filipino students, the Canadian Embassy held its first flat wire in Canada Fair in the Philippines early this year. who seem at a loss as to how to raise $600?million for construction and operations without causing drivers to divert and clog nearby streets.

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