For those outside the UK, the Crossrail project is a mega-project upgrade to the London metro area’s subway system. The tunneling portion of the project will consist of 21-km of twin-bore tunnels excavated by eight closed-faced tunnel boring machines, six of which will be earth pressure balance machines (EPBMs). The UK’s Geological Society has published an interesting article on the geology of the crossrail project. Some of the geological and geotechnical challenges of the project include the famous London Clay, sensitive structures, faults, and rapid transitions between permeable and relatively impermeable formations creating potential water pressure issues. [Source: Geological Society. Image: Geological Society]
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Feb. 7 Bertha update: Two factors contributed to tunnel stoppage
WSDOT released an update on February 7 with some conclusions regarding the blockage that has stopped the Alaska Way Viaduct Tunnel Boring Machine, Bertha’s progress since December 6. Now they don’t think it was necessarily the well casing after all.
They cite two factors that contributed to the blockage. First, the cutterhead was clogged with material. You can see an cool short video of a worker unclogging the cutterhead. Not terribly dramatic, but still cool. The second factor was increased temperatures inside the equipment. STP discovered damage to a seal that protects the machine’s main bearing. They are still determining how the repairs will be done.
If you want to follow the chronology of this issue, read below for summaries and links to previous updates from WSDOT. And Check out the videos too! [Source: WSDOT]
Boston’s Big Dig Finally Complete
The $14.8 billion project that has constructed a dizzying array of underground highways, bridges, ramps and tunnels in the middle of Boston has finally ended. The end of 2007 apparently was also the end of the Bechtel/Parsons Brinkerhoff joint venture that designed and built the project. More… (Photo by brewrat)