And a train was actually hit! Fortunately it was stationary on the tracks, but it crushed the side panel of the driver’s carriage. Neither the driver nor any passengers were injured in the incident. The drill rig was drilling to install ground source heating or geothermal heating for a hotel when at a depth of 20 to 25 meters (65 to 82-ft), the drillers noticed that they lost resistance when they punched through the subway tunnel. Upon withdrawing the drill stem, they were missing the bottom 2.5-m according to a local police official. Story at The Local. (Photo of N.Y. Subway from runnx)
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Cologne Tunnel Collapse: Investigations Focus on Tiebacks and Groundwater
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)
Bertha tunnel-boring machine arrives in Seattle
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It can only happen if the co. is highly unprofessional.
thnks
nk agarwal
Tunnelling Engineering 🙂