| ▲ | First tunnel element of the Fehmarnbelt Tunnel immersed(arup.com) |
| 77 points by robin_reala 4 days ago | 17 comments |
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| ▲ | jedberg 41 minutes ago | parent | next [-] |
| Today I learned the Transbay Tube is the longest immersed tube in the world. Given that it opened in 1974, it presumably has held that record for 52 years! |
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| ▲ | yrcyrc 7 hours ago | parent | prev | next [-] |
| Very nice video explainer
https://public.skyfish.com/p/sundogbaelt/2675422/70675433?pr... |
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| ▲ | Animats 37 minutes ago | parent [-] | | 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/ | | |
| ▲ | vanderZwan 27 minutes ago | parent [-] | | 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. |
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| ▲ | Liftyee 8 hours ago | parent | prev | next [-] |
| I'm amazed that engineers can make submerged tunnels work and that leaks don't (literally) sink the whole plan. |
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| ▲ | ianburrell 7 hours ago | parent [-] | | The Transbay Tube carrying BART across the bay is immersed tube. The sections were welded together by divers. The sections were filled with water and then pumped out. Fehmarnbelt tunnel sections are concrete. I couldn't find how they are connected by concrete would make sense. | | |
| ▲ | imglorp 7 hours ago | parent | next [-] | | A video posted in another thread says the segments are sealed with bulkheads, floated into position, submerged by allowing water into a ballast section, dropped into place , aligned with pins, drawn to the next segment with hydraulic jacks, and sealed to it with rubber gaskets. Then the bulkheads can be removed. The gaskets also allow for some thermal expansion. I'm curious what the lifetime of those gaskets might be and how you might maintain them. | | | |
| ▲ | bloggie 4 hours ago | parent | prev [-] | | Here’s a fun video about how one sunken tunnel was built in Vancouver back in the 50s. https://youtu.be/A1igKk8eK0M |
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| ▲ | readthenotes1 7 hours ago | parent | prev [-] |
| 52.6B krone for 18 km 8B USD for 11 miles CACHSR IOS 36B USD for 171 miles. The Merced to Bakersfield IOS looks like a bargain on a distance basis. I have no idea of the carbon offset or passenger time saving versus flying of course |
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