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That is a resasonable question, but I think it would have been mentioned if it is a significant issue. Tunnelling through the Alps is also bedrock tunnelling,
by mannykannot 6y ago
That is a resasonable question, but I think it would have been mentioned if it is a significant issue.
Tunnelling through the Alps is also bedrock tunnelling, and not near-surface bedrock, either. The Gothard Base Tunnel, completed in 2016, cost $12 bn and is 35.5 miles long [1].
The London Crossrail tunnels are not in bedrock, but there was some significant engineering in threading around and between existing infrastructure, and in protecting it. For all I know, bedrock tunnelling may be easier.
[1] https://www.latimes.com/world/la-fg-switzerland-rail-tunnel-20160601-snap-story.html https://www.latimes.com/world/la-fg-switzerland-rail-tunnel-...
- fastball 6y agoPresumably tunneling through a mountain is much easier than underground because either end is just open. Very easy to get your boring machine into position / service it when needed (by just pulling it back out into the open air). Also probably less issues with damp, etc.
- mauvehaus 6y agoTunnel boring machines (TBMs) bore a gross diameter hole that's then lined (often with concrete segments) for support. The net diameter of the hole behind the TBM is less than the diameter of the TBM, particularly the shield, which is the business end. Maintenance is done in place. Fun Chunnel fact: when the TBMs driving from England and France met, they drove one below the other and abandoned it in place. The other was dismantled and removed in pieces.