Fixing a 7,000-Ton Drill 101
An anonymous reader writes: At the end of last year, we discussed Bertha, the world's largest tunnel boring machine. During an effort to drill a viaduct beneath downtown Seattle, the machine — clocking in at 7,000 tons, 57.5 feet in diameter, and 326 feet long — got hamstrung by an 8-inch-diameter steel pipe. The complexity and scope of the repair plan rivals that of the project itself. "The rescue operation (workers call it "the intervention") began in late spring with construction on the shaft to reach Bertha. Workers have been sinking pilings in a ring to prevent the shaft from collapsing, using 24,000 cubic yards of concrete — enough for a medium-size office building. Once that ring is complete, digging on the shaft will start. When the shaft is ready, Bertha, which is damaged but still operational, will be turned back on so she can chew through the concrete pilings to reach the center of the shaft. There, the machine will rest on a cradle where workers can detach the front end and hoist it out." That detachable front end? It weighs about 2,000 tons by itself. The repair bill is estimated at about $125 million.
Bad seals on the bearings and master bearing (Score:5, Interesting)
Actually, something else is causing the seals to fail on the bearings and master bearing. The sampling pipe was the original theory but it could not account for the damage being done.
FTFA “Contractors are not entirely sure what’s happening to the seals. They’re letting sand in, which is not good,” said Matt Preedy, deputy Highway 99 administrator for the state Department of Transportation (DOT). “Either you’ve got gaps somewhere, or you’ve got cracks in the seals.”
http://seattletimes.com/html/l... [seattletimes.com]
Basically, our water front soil make up is not ideal. Much of the Seattle water front is fill dirt from various late 19th century and early 20th century projects around Seattle. Much of the path Bertha is taking underground is lined with caissons to keep the liquid dirt at bay.
The Republicans that rule this state... (Score:0, Interesting)
are doing everything they can to screw Seattle. They hate us, and they want us to suffer with horrific traffic by making every project ridiculously expensive. For example, they made our light rail cost over $5 billion. With the few people that ride it each day because they wouldn't let us put it in places that make sense, we could have given every daily rider $166,000 each and come-out cheaper. With this project, they wouldn't allow it to be put in a sensible location so there are going to be fewer drivers using it than the tunnel it replaces. Also, they're going to charge so much that only wealthy people can afford to use it so that us normal people are going to be stuck with surface streets. This is the same tactic they took with the 520 bridge. It is one of two ways into the city from the east, and the Republicans closed it to minorities and the poor.
Re: Bad seals on the bearings and master bearing (Score:0, Interesting)
Which literally everyone knew before this started. This entire project , corrupt gov, and corrupt contractors can go to hell. Stupidest idea since we built that classless ferris wheel on our front porch. /seattleinfrastructuresucks
Re:Virtual tour (Score:3, Interesting)
Perhaps Sealttle should take a lesson from the Crossrail project in London. There has been 3 * 1 hour long TV progs about the building of the tunnels recently broadcast.
They were called "The Fifteen Billion Pound Railway".
As a Civil enginner and having worked on the Channel Tunnel, I was amazed at the progress that has been made since the late 1980's in tunnelling. The bits where they had to thread the TBM between existing tunnels at Tottenham Court Road was fantastic.
I'm sure the programmes are on the internet somewhere.