Building the Tunnel Behind Bertha

The latest information to come out of the collapse of a subway tunnel excavation in Cologne, Germany is that investigators are evaluating the ground anchors or tiebacks that were holding open the subway tunnel excavation. There doesn’t appear to be much information available to the public yet, and the New Civil Engineer article mostly quoted academics saying an anchor failure “could” have caused the collapse. Apparently at the time of the collapse, the excavation had reached the bottom depth after the slurry walls had been constructed along with the ground anchor system. Crews were supposedly working on the base slab which would have undoubtedly stiffened up the whole system. For what its worth, an anonymous comment left at the bottom of that article indicated that after half of the debris had been excavated, the diaphragm walls were still intact and without apparent displacement. So what other theories have been floated? Read on for more info.  (Image Credit: New Civil Engineer)

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The Port Authority of Allegheny County (Pittsburgh, Pennsylvania) has a major transit improvement project dubbed the North Shore Connector. Its main components are twin bored tunnels 1.2 miles long that will connect the Port Authority’s Light Rail Transit system, the T, 1.2 miles from the Gateway Subway Station underneath Stanwix Street and the Allegheny River to the North Shore. It will travel under the river and provide three new stations and allow for future improvements beneficial to future development and continued downtown revitalization. The $435 million project is making news recently for cost increases, drawing comparisons to Boston’s Big Dig much to the dismay of the Port Authority. Read on for project maps, links and more info. 

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Seven new design contracts were issued today for the Crossrail project including four central London Stations and three significant portals. According to the New Civil Engineer, the project is being called "Europe’s Largest Construction Project". […]