Just 10m of drill and blast left on Gotthard Base Tunnel

The Seattle Times (hat tip to ASCE SmartBrief) has reported that seven voids have been discovered above the Beacon Hill Tunnel with one opening up at the ground surface. The tunnel is being constructed by Sound Transit, the area’s transportation agency as part of a roughly $2.6 billion (yep, billion) light-rail project connecting downtown Seattle with the University of Washington and SEA-TAC airport. The voids were a result of running sand pockets in the otherwise stable clay units that were encountered by the tunnel boring machine or TBM. These voids migrated up like a chimney with one reaching the surface, almost 160-ft above the tunnel. This void was apparently 21-ft deep and opened up in a resident’s front yard and could have easily swallowed her up as she noticed it while gardening. The other voids were discovered at a depth of 20- to 65-ft below the ground surface. More after the break. (Illustration from Seattle Times)

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[Updated November 17, 2009] A few new posts from Ontario-geofish [/Updated]

Those with interest in rock mechanics and tunneling might be interested in this project. The Ontario Power Generation (OPG) company is the owner of a $600M (Canadian) construction project to create a third hydro power tunnel under Niagara Falls.  Apparently the project is having all kinds of problems with overbreak in some very difficult tunneling conditions which means very slow progress and big $$ overruns. (Photo from niagarafrontier.com)

I’ve been meaning to post something on this project for some time. I admit that my perspective is biased by the viewpoint you can find on the Ontario-geofish blog. I’ve mentioned Harold Asmis before, he’s the owner of the OG blog, and a former OPG employee if I understand correctly. He left OPG for a career doing geophysics and earthquake engineering for the Nuclear Power industry in Canada.  I highly recommend his blog, he has great insight into tunneling, earthquakes, siting of nuclear power plants not to mention opinions on all kinds of other things.  His writing style is very colorful and entertaining as well.

So, Harold has written a whole series of blog posts on the Niagra Tunnel project, including a 5-part series entitled "The Disaster of the Niagara Tunnel" and a 4-part series called "Niagara Tunnel: doing it Right".  He is not directly involved with the project, but his long career with OPG and related disciplines gives him some great insights.  I’ve collected a list of some of his blog posts on the Niagara Tunnel project as well as a few other links about the project. Click through for the good stuff.

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City officials and residents in Amsterdam, Netherlands are looking at the recent Cologne tunnel collapse and wondering if the construction of their fourth metro line could have similar problems. Although the tunnels themselves have not […]