4 ms·
First tunnel element of the Fehmarnbelt Tunnel immersed
- Liftyee 5mo agoI'm amazed that engineers can make submerged tunnels work and that leaks don't (literally) sink the whole plan.
- ianburrell 5mo agoThe 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 5mo agoA 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 5mo agoI figure once you join them, you could also apply waterproofing to the outside as well, no?
- lmm 5mo agoMaybe. What would that look like, adding more gaskets on the outside? That sounds even harder to maintain since the only way to get access is diving.
- deleted 5mo ago[deleted]
- euroderf 5mo agoSome kind of goop that would get very slowly squeezed into gaps by water pressure ?
- usrusr 5mo agoSealing is really not that difficult if you have access to the high pressure side. The hard part is identifying the location of the leak. In sum, this means that they have to absolutely nail it, on the first attempt, for the bottom part that is resting on the sea floor. If they can to that, the rest of the circumference will also be so good they don't have to even think about fixability.
- tokai 5mo agoThe sections are laid in a trench and covered by sediment. There's not going to be any routine maintenance by divers.
- SoftTalker 5mo agoThe "ballast sections" may act as bilges, so that any leaks will accumulate there and can be pumped out. 100% water-tightness is not essential. Occasional re-grouting/caulking of the joints may be good enough.
- poizan42 5mo agoThey are GINA gaskets[0], they were supposed to last 120 years[1], but it has recently been shown that they may deteriorate faster than previously expected due to being under constant compression[2][3] [0] https://www.trelleborg.com/en/marine-and-infrastructure/media/in-the-news/tailor-made-sealing-systems-for-the-fehmarnbelt-immersed-tunnel https://www.trelleborg.com/en/marine-and-infrastructure/medi... [1] https://www.trelleborg.com/marine-and-infrastructure/-/media/marine-systems/resources/case-studies/downloads/keeping-immersed-tunnels-watertight-for-120-years.pdf?rev=30fcb4a6a6f04555afe7c96290dae4ab https://www.trelleborg.com/marine-and-infrastructure/-/media... [2] https://www.sciencedirect.com/science/article/abs/pii/S0886779825008909 https://www.sciencedirect.com/science/article/abs/pii/S08867... [3] https://dailygalaxy.com/2026/03/rubber-used-in-undersea-tunnels-decay-fast/ https://dailygalaxy.com/2026/03/rubber-used-in-undersea-tunn...
- imglorp 5mo agoInteresting! The spec sheet actually says 170 years but maybe they add some safety factor. https://www.trelleborg.com/marine-and-infrastructure/-/media/marine-systems/sustainability/gina-gasket-mrpi-epd-trelleborg.pdf?rev=06d95e35d0a24613a6ee081b8c83c015 https://www.trelleborg.com/marine-and-infrastructure/-/media...
- bloggie 5mo agoHere’s a fun video about how one sunken tunnel was built in Vancouver back in the 50s. https://youtu.be/A1igKk8eK0M https://youtu.be/A1igKk8eK0M
- tekla 5mo agoThe almost insane genius Brunel and the insane Thames Tunnel Project which was deep enough that workers suffered the bends. https://en.wikipedia.org/wiki/Thames_Tunnel https://en.wikipedia.org/wiki/Thames_Tunnel
- readthenotes1 5mo ago52.6B 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
- bradchris 5mo agoWell, 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-angeles-metro-d-line-extension https://www.latimes.com/california/story/2026-05-07/los-ange...
- Melkman 5mo agoThey 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.
- readthenotes1 5mo agoOf course they are comparable. They are both mechanisms to get people from point A to point B
- looperhacks 5mo ago1USD = 6,35 DKK
- lukan 5mo agoThe building of this tunnel will likely create way more CO2, than can be saved by providing a more direct route and avoiding ferries (german source ... and very critical of the project) https://www.nabu.de/umwelt-und-ressourcen/verkehr/verkehrsinfrastruktur/fehmarnbeltquerung/28486.html https://www.nabu.de/umwelt-und-ressourcen/verkehr/verkehrsin... Personally I like the concept of having a more direct access to scandinavia and see lots of other positive long term effects.
- yrcyrc 5mo agoVery nice video explainer https://public.skyfish.com/p/sundogbaelt/2675422/70675433?predicate=created&direction=desc https://public.skyfish.com/p/sundogbaelt/2675422/70675433?pr...
- Animats 5mo agoHere'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 https://www.youtube.com/watch?v=247JT7ctQ_I [2] https://bethlehemshipyardmuseum.org/ https://bethlehemshipyardmuseum.org/
- vanderZwan 5mo agoIt'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.
- peterfirefly 5mo agohttps://en.wikipedia.org/wiki/Post-glacial_rebound 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.
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- jedberg 5mo agoToday 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!
- BretonForearm 5mo agoThat horrible website overrides web page scrolling and disables pinch zoom. Bad!
- nottorp 5mo agoFirst it gives you a popup saying i'm not in the US and would I like to visit the global site? In my experience that means they send me to the other site that doesn't even have the article i clicked to, or even if it has it they can't redirect me to it.
- swores 5mo agoVery much depends on the site - certainly there's plenty that are annoying in the way you describe, but there's also plenty (I wouldn't be surprised if either side were the majority) that will take you to the exact same content on the more local version of the site.
- robin_reala 5mo agoThe official site’s news story is at https://femern.com/press/news/the-first-element-of-the-fehmarnbelt-tunnel-successfully-immersed/ https://femern.com/press/news/the-first-element-of-the-fehma... . But that wasn’t available when I originally submitted this (which was a few days ago, it just hit the second-chance pool).
- usrusr 5mo agoCan anyone from the region comment on the status of plans for the landside linkup on the German side? Last time it made the press it was because the project was at risk of seeing the Danish tunnel finished before Germany could tell not even when but if a linkup would ever make it across bureaucratic hurdles. Almost like a Darien Gap made exclusively of red tape.
- logifail 5mo agoYou mean like the Brenner Base [Rail] Tunnel which will connect Austria and Italy? Germany seems to be stuck at the "studying" stage before they improve the relevant rail links on the Grafing–Rosenheim–Kufstein route. https://en.wikipedia.org/wiki/Brenner_Base_Tunnel https://en.wikipedia.org/wiki/Brenner_Base_Tunnel
- deleted 5mo ago[deleted]
- grumbelbart2 5mo agoThe exact same thing is happening with the Gotthard Base Tunnel. Switzerland has completed it almost 10 years ago, Germany still hasn't finished the links. It is combination of the German planning system, which allows the processes to be stretched out due to objections, and spineless politicians who don't really want to commit to a route and kick the can down the road (because whatever they do, someone will be angry; but voter's don't really make you responsible if the link isn't built or is delayed).
- usrusr 5mo agoWhen the iron curtain fell, there were big plans and a formal contract about modernizing the rail link between Prague and Nuremberg (a hugely important connection on the days of Charles IV). The Czech side eventually stopped electrifying their parts when they realized nothing happened on the other side of the border. These days, Deutsche Bahn is operating a _bus connection_ between the cities. It seems like they are solely focused on beating imaginary Autobahn times between a selected set of major German cities, and consider everything else a nuisance...
- yxhuvud 5mo ago> The Fehmarnbelt Tunnel will complete the high-speed rail connection between Stockholm and Hamburg. Not really, mostly cause Sweden don't want to build high speed rail, even when EU would have paid for a big share of it.
- robin_reala 5mo agoMost of the Malmö <-> Stockholm line is 200km/h plus (see https://commons.wikimedia.org/wiki/File:Map_of_Swedish_railways.svg https://commons.wikimedia.org/wiki/File:Map_of_Swedish_railw...) and that’s generally seen to be where “high-speed” starts. But yes, they could do a lot better.
- whizzter 5mo agoGetting to 200 was mostly a matter of upgrading tracks that needed maintenance anyhow in the 90s, in the 90s however cargo traffic wasn't causing as many disruptions and congestion as today and the talks about "new exclusive" lines is mainly meant to shift air-traffic to faster AND non-congested lines, but new lines are far more expensive/prohibitive both due to new land requirements and making it a "big-bang" build.
- whizzter 5mo agoThat "minor" detail seems to have been outside of all popular reporting I've read on the subject, any links to how large a part the EU would've contributed?
- yxhuvud 5mo agoIt was in the news (at the very least DN) a couple of months after the current government scrapped the plans for high speed trains. So Dec-Jan 22/23 or so. Googling for it to find the details have proven to be hard, so I can't say for sure if those articles referred to grants part of the CEF program, but very probably so. And I also obviously can't give any numbers without refinding those articles. But it was a fairly large share, based on memory. EDIT: Found it! https://www.dn.se/ekonomi/regeringen-bad-eu-andra-tagkartor-missar-chans-till-miljarder-i-stod/ https://www.dn.se/ekonomi/regeringen-bad-eu-andra-tagkartor-... mentions it and that the possible numbers were really high, upwards 100GSEK or more. But only 'possible' numbers and not granted ones, so who knows how much it would have been in practice.
- alex_duf 5mo ago[flagged]
- sveme 5mo ago"Immersed". The channel tunnel was bored below the sea floor.
- simonebrunozzi 5mo agoThere's no need to write "are you drunk?". Anyone can write a typo, or simply be mistaken. Treat people respectfully.
- alex_duf 5mo agoAgreed, I got carried away
- Towaway69 5mo agoI wonder what the relationship is between the word engineering in the sense used here and software engineering? I am amazed how bad software engineering has become with constant updates of software because of “improvements” or because there has to be constant release cycle else the software is unmaintained or bad. While this kind of engineering is designed to be untouched for the next 15 to 30 years. Minimal maintenance is needed and certainly the concrete doesn’t need updating every second week because concrete has suddenly “improved” or there was a bug in it. It’s become the norm to release bad software and fix it later, I hope this norm does not make it to real engineering.
- mmillin 5mo agoDo you have a source for how little maintenance this will need? I imagine there will be teams of people continually employed for regular maintenance and operations. Concrete does develop “bugs” in the form of cracks, chips, or other damage that needs to be repaired. While software engineering certainly deals with different constraints, I don’t think this is a fair comparison. When stakes are low (as they are for most software engineering), different precautions are appropriate. The aerospace or financial software engineering worlds might be more comparable here, and the engineering for those systems looks quite different as a result. See also: https://www.jerf.org/iri/post/2026/programming_is_engineering/ https://www.jerf.org/iri/post/2026/programming_is_engineerin...
- Towaway69 5mo agoDefinitely I am making a broad assumption with many specifies where one can say "but what about X,Y,Z". Certainly, there are buildings that fall down and bridges collapse but what is the trend? Is software engineering getting better or worse? From the linked article: > And I would say that the success of AI coding agents has proved once and for all that we had successfully built an engineering discipline so strong that we are also the first discipline that has been able to successfully run AI at large scale within our discipline. Yet we have no real clue how AI works or how to debug it, it's a brute force solution to everyday problems. Daily there are new examples of AI "escaping" its enforced cage. Why? Why doesn't AI "just work"? Because we don't truly understand AI. I think AI is exactly the opposite to "true" engineering where one understands the system and can reproduce it. After all, retraining the AI will probably give you a completely different AI even if the training data was the same.
- teekert 5mo agoHmm, website owners can apparently mess with my settings and make their site "smooth scrolling". Ugh. It's like having a nightmare where I'm trying to scroll as hard as I can but I feel like I'm scrolling through mud. It actually feels like they have a speed limit to scrolling, I'm used to giving my MX Master 3S a big spin and being at the bottom of a page near instantly, here it takes time.
- TazeTSchnitzel 5mo agoOn my mobile device, it's like they've made the scrolling accelerated and slippy, as if it's on ice suddenly. It's very unpleasant.
- lxgr 5mo agoSee how dangerous road conditions out in the open can be? This won't happen to you in a tunnel! Consider commissioning one with us today :)
- internet_points 5mo agothere must be some way to make the browser disable it?
- Skwid 5mo agoIf you disable javascript it scrolls normally. There's also no text, or images, but you can scroll past all the pretty background colours
- tocs3 5mo agoI worked for a company on a job in New York harbor surveying a 9ft diameter sewage tunnel that runs from Newark under Bayonne to New York Harbor (there is a vent near the little lighthouse you pass on the Staten Island Ferry). There was concern that some of the dredging would lighten the load over the tunnel and the tunnel would pop out of the ground.
- TazeTSchnitzel 5mo agoThis is very exciting if you live in the Copenhagen–Malmö area. Currently it takes 5 hours from Copenhagen to Hamburg, and 8 hours if you want to get to Berlin. With this tunnel done, I believe Copenhagen to Hamburg will be less than three hours. Suddenly a weekend trip to Germany by train looks more practical. The train is very nice right now, but you need to set aside a day for travel, in both directions. It's a shame that the legacy of the Cold War means that Hamburg is “closer” by rail than Berlin, even though if you look at a map you can see it shouldn't be. If they had built a tunnel to Rostock, things would have been different…
- dasKrokodil 5mo ago> With this tunnel done, I believe Copenhagen to Hamburg will be less than three hours. Even when the tunnel will finally be done, Deutsche Bahn will find creative ways to make it take five hours again.
- medvidek 5mo agoI recently took the first direct train from Prague to Copenhagen which was expected to take 13 hours from PRG to CPH (normally it should be 11 but there is a construction on the high speed line between Berlin and Hamburg so we had to take a detour through Uelzen). The train left the Czech Republic with 0 minutes delay. Long story short, we crossed the German-Danish border more than FIVE hours later than the original plan. And it wasn't even in the same physical train, the original one got cancelled from Hamburg because of the huge delay we already had. As for the reason of the delay, at first it was just German "normal" state of things, we left Bad Schandau (the first German station) on time, got to Dresden with 5 minutes (still "on time" according to DB), then without any visible reason got 20 minutes on approach to Berlin where there were so many people on the platform that it took some other twenty minutes for the passengers to get on and off. When we arrived to Luneburg, the train stopped and after an hour or so the crew said that there is a problem on the line to Hamburg so we'd have to take another detour (from a detour!) and go through Hannover which added several hours to our delay. On approach to Hamburg we already knew that we'd have to transfer to a Danish train there, which thankfully went pretty fast and we left for Schleswig, where our train stopped again, this time because of a "fire in the vicinity of the tracks". After another two or three hours that it took the firefighters to realize that nothing was actually burning, we finally left Germany and the rest of the trip went just fine and we did not gather any additional delay in Denmark, arriving to Copenhagen in the middle of the night (instead of the original 7:30pm). TL;DR: Sänk ju for trävelin wiß Deutsche Bahn! Czech media even wrote[1] about how the train failed to get to its destination. [1]: https://zdopravy.cz/prvni-primy-vlak-z-prahy-do-kodane-skoncil-v-hamburku-premieru-zhatila-nemecka-infrastruktura-280556/ https://zdopravy.cz/prvni-primy-vlak-z-prahy-do-kodane-skonc...
- rbanffy 5mo agoAnd here I am measuring the distance from Dublin (Ireland) to Holyhead - would be ok for fast rail, but then it's between 3 to 5 hours of rail to London. I wonder if Ryanair pays rail companies to offer poor service.
- mprev 5mo agoIsn't the issue the depth of the Irish Sea at the point where Scotland and Ireland are closest? It gets to around 1,000 ft deep there (roughly 5x where the Channel Tunnel goes) and has a bunch of unexploded WW2 bombs dumped there, too. Then Dublin to Holyhead is, what, 70 miles? That's twice as long as the Seikan tunnel, which I think is the world's longest under sea tunnel.
- rbanffy 5mo agoI think it isn’t that deep - last time I checked it was reasonable, but you make a good point about unexploded ordnance. Building it would be a thrill.
- Tade0 5mo ago> I wonder if Ryanair pays rail companies to offer poor service. I think the rail companies do it free of charge and Ryanair is happy to accept this business proposition.
- dredmorbius 5mo agoSuch proposals exist under the rubric "Irish Sea Bridge": <https://en.wikipedia.org/wiki/Irish_Sea_Bridge https://en.wikipedia.org/wiki/Irish_Sea_Bridge>. The four leading crossing options would be the Kintyre (most northerly), Galloway, Irish Mail, and Tuskar (most southerly) routes. Irish Sea depths (notably Beaufort's Dyke), and unexploded and chemical ordinance, are principle concerns.
- rbanffy 5mo agoThat’d be awesome. What is the current tallest ship that could damage a bridge? You can count on someone eventually doing that.
- Aardwolf 5mo ago"It looks like you're trying to visit our US site, but you're not based in the US. If you'd prefer to visit our global site, please click on 'Global site' below, alternatively if you wish to continue to the US site, please click 'Continue'." Do they want me to read their article or not? It shouldn't matter where I am for that Are they aware this question invokes anxiety to the visitor because many websites will show a different generic page instead of the desired one when clicking one of the options?
- pixl97 5mo ago> It shouldn't matter where I am for that Ah, an old person on the internet from the days before it was balkanized. How great it was to live in that time that no longer exists.
- upcoming-sesame 5mo agohow do you protect something like this from someone deciding to blow themselves up in the middle of the tunnel?