First tunnel element of the Fehmarnbelt Tunnel immersed

yrcyrc•about 1 hour ago

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

Liftyee•about 2 hours ago

I'm amazed that engineers can make submerged tunnels work and that leaks don't (literally) sink the whole plan.

ianburrell•about 1 hour ago

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•about 1 hour ago

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.

bobthepanda•19 minutes ago

I figure once you join them, you could also apply waterproofing to the outside as well, no?

readthenotes1•about 2 hours ago

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

Melkman•about 1 hour ago

They are not really comparable are they. One is a rail connection over land and the other is a 130ft deep tunnel for rail and road traffic.

bradchris•about 1 hour ago

Well, if we’re comparing CA infra costs, for a more 1-1 comparison you can look at the $9.7B Los Angeles is spending on building out a long-awaited subway line (phase 1 of 3 opened Friday!) and see how tunneling underwater looks like a bargain in comparison.

https://www.latimes.com/california/story/2026-05-07/los-ange...

First tunnel element of the Fehmarnbelt Tunnel immersed

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