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Comment by yrcyrc | Hacker News Reader

Very nice video explainer https://public.skyfish.com/p/sundogbaelt/2675422/70675433?pr...

Here's a similar video for BART's Transbay Tube, which was built in a similar way.[1] The major differences come from building in an earthquake zone. The Transbay Tube is mostly steel, rather than concrete, for flexibility. There are expansion joints. And the Transbay Tube sits on a gravel and sand base rather than hard rock, on purpose.

The Transbay Tube sections were built in the Bethlehem Steel shipyards in San Francisco. A museum opens this month to commemorate that shipyard. It's in Dogpatch in SF, if you know the area. The shipyard still has a submersible drydock, but it hasn't worked in ten years and will be demolished soon, hopefully before it sinks.

The SF Bay Area once had far more heavy industry than most people realize.

[1] https://www.youtube.com/watch?v=247JT7ctQ_I

[2] https://bethlehemshipyardmuseum.org/

It's not in an earthquake zone, but isn't the Scandinavian continent still rising at a surprisingly fast rate? I wonder if that could affect the engineering of the Fehmarnbelt tunnel, in an "in x years one end of the tunnel will have risen n centimeters compared to the other end" way. It's probably such a small amount it's well within levels where regular maintance will cover it anyway, but I'm still curious.

https://en.wikipedia.org/wiki/Post-glacial_rebound

Not so much that far South in Denmark, but the wikipedia article mentions a lake in Sweden that has its shores rebounding (moving upwards) at about 2mm per year. The Northern side moves faster so it is effectively tilting.

Pretty cool dredge display @1:16. How does it work? Is it just sonar?

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