The cover story of the November 2012 Civil Engineering Magazine is about the incredible cantilevered pedestrian walkway known as the Cliffwalk, located some 300 feet above the Capilano River Valley in Capilano Suspension Bridge Park near Vancouver. This amazing structure is a feat of rock engineering as well as structural engineering, fabrication and construction (among other things). Famed geological engineer Duncan Wyllie, who literally wrote the book on Foundations on Rock, was the rock engineer on the project. The geotechnical engineers rappelled along the cliff face to perform structure mapping. The rock bolts in the granite cliff were up to 18 feet long, and a total of 1,673 feet of rock bolting was used. The geotechnical design also had to consider rockfall potential above the walkway. The excellent video below shows the entire process of construction of the Cliffwalk…it’s well worth the 6 or 7 minutes! [Source: Civil Engineering Magazine. Image: Capilano Suspension Bridge Flickr Stream]
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City of Vancouver sues over failed shoring
The City of Vancouver is suing a developer, excavation contractor and their consulting engineer for the costs of repairs, overtime for city employees and lost revenue from parking meters etc stemming from an apparent failure of a shoring system that formed a 30-meter sinkhole. No mention of the developer’s name or the engineer, but the contractor was Matcon Excavation and Shoring. The site will be the future home of high-rise condominiums…if the City lifts it’s stop work order.
The failure of the shoring caused a break inf a 20-cm water main ultimately flooding the site. It also necessitated the closure of the adjacent street. Of course this invites the whole chicken or the egg scenario. The defendants will probably argue that the water line failed first causing the failure of the shoring, but of course the City Engineer, Tom Timm was not shy about fingering the shoring as being deficient.
"It’s some kind of a failure of the shoring system . . . either a design issue or the way it was put in place."
Rockfall Hazards Overview by Colorado Geologic Survey
The Colorado Geologic Survey has a very comprehensive overview of the geologic hazard of rockfall in all its many forms in their latest issue of RockTalk newsletter. The entire 24-page newsletter is devoted to various aspects of the problem, mitigation options and case studies all with excellent photos. I highly recommend that you check it out. Click through for the link. (Photo by CGS)