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Cologne Tunnel Collapse: Investigations Focus on Tiebacks and Groundwater PDF Print E-mail
Written by Randy Post   
Tuesday, 24 March 2009 13:18

image 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)

The area is approximately 300-m from the Rhine River, and groundwater is very shallow. As noted in another NCE article, the contractor constructed 15 dewatering wells when only 4 were approved. Additionally, the pumping rate being used was 750 m^3/hr, or nearly double the 450 m^3/hr it was pumping in December of 2008. Clearly the groundwater is one component of the failure, but it does not appear that there is sufficient evidence to say exactly what role of the groundwater was or if the shoring walls did in fact fail and lead to the collapse of the Cologne historical archives and the deaths of two people.

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Last Updated on Tuesday, 24 March 2009 13:21