First tunnel element of the Fehmarnbelt Tunnel immersed

https://www.arup.com/en-us/news/first-fehmarnbelt-tunnel-element-lowered/

by robin_reala • 3 months ago

157 95 3 months ago

Liftyee• 2 months ago

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

ianburrell2• 2 months 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.

imglorp2• 2 months 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.

bloggie• 2 months ago

Here’s a fun video about how one sunken tunnel was built in Vancouver back in the 50s. https://youtu.be/A1igKk8eK0M

tekla• 2 months ago

The 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

readthenotes12• 2 months 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

bradchris• 2 months 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...

Melkman• 2 months 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.

readthenotes12• 2 months ago

Of course they are comparable. They are both mechanisms to get people from point A to point B

looperhacks• 2 months ago

1USD = 6,35 DKK

lukan7• 2 months ago

The 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/verkehrsin...

Personally I like the concept of having a more direct access to scandinavia and see lots of other positive long term effects.

gmueckl2• 2 months ago

I really hate how German environmental activists resort to hyperbole and alarmist language by default when voicing concerns. This only makes it harder for me to take them seriously.

And then there is this tried and true tradition of commissioning studies with the sole intent to support a predefined viewpoint rather than taking an unbiased approach. This makes it so hard to trust any information when political arguments become heated.

To make the connection back to the tunnel: it consumes a huge amount of concrete and that releases the associated amount of CO2. Thisnpart is fairly easy to estimate. But estimating the impact on traffic emissions is fraught with issues. There are so many assumptions about lifetime, amount of traffic, types of vehicles that I can easily imagine the error bars to stack up to the point where a little tuning of model parameters gives just about any desired result.

mrweasel• 2 months ago

From a Danish perspective I don't really see any positive long, or short, term gains from the Fehmarn tunnel, but I also live in the wrong part of the country.

This is a tunnel for Sweden, Norway and Copenhagen, it's moving the center of everything in Denmark closer and closer to the center of Copenhagen, completely disconnecting the rest of the country. A few days ago a new train start running Copenhagen to Oslo, a seven hour trip. That's the same time it takes me to get to Copenhagen by train within Denmark. Everyone is happy that you can "Get on the train and just pop to Hamburg, Berlin or Prag", but you can't, only if you happen to live in a few select spots does that work. It's a multi-day journey with a layover within the country if I want to leave by rail.

Internationally this is a great project, internally in Denmark, it's going to make international train travel worse for the majority of the country.

yrcyrc• 2 months ago

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

Animats• 2 months ago

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• 2 months ago

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.

orbital-decay• 2 months ago

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

jedberg• 2 months ago

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!

BretonForearm• 2 months ago

That horrible website overrides web page scrolling and disables pinch zoom. Bad!

nottorp• 2 months ago

First 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• 2 months ago

Very 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_reala3• 2 months ago

The official site’s news story is at 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).

usrusr3• 2 months ago

Can 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• 2 months ago

You 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

grumbelbart2• 2 months ago

The 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).

usrusr3• 2 months ago

When 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...

shellfishgene• 2 months ago

It's not really clear, the German part was going slower than the tunnel, but now that the tunnel is also delayed by at least 2 years, who knows maybe they are in sync again ;). The road link seems to be going much faster than the rail link on the German sinde, which won't be done before 2032.

wasmitnetzen• 2 months ago

The tricky part will be the the train tunnel on the other end of Fehmarn, the current best guess for the finishing date is 2032[1]. They haven't started building yet[2], so I wouldn't put a lot of trust in that number.

[1] https://de.wikipedia.org/wiki/Fehmarnsundtunnel [2]: https://www.anbindung-fbq.de/streckenabschnitte/sundquerung....

yxhuvud2• 2 months 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_reala3• 2 months ago

Most of the Malmö <-> Stockholm line is 200km/h plus (see 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.

whizzter2• 2 months ago

Getting 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.

whizzter2• 2 months ago

That "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?

yxhuvud2• 2 months ago

It 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-... 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.

Towaway694• 2 months ago

I 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• 2 months ago

Do 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.

Towaway694• 2 months ago

Definitely 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.

mschuster912• 2 months ago

Do you have a source for how little maintenance this will need?

In Germany, twice a year inspection is mandatory for infrastructure [1] but this is only a visual inspection. Once every 6 years you got a large inspection [2] that includes a full go over everything including functionality checks plus a review of documentation (if it is still up to code) and of accident documentation, as well as a "knock test" on every m² of surface [3]. Fire safety systems are checked every quarter [4].

And out of these reports then you get action items. Depending on the severity of findings, it can be anything from "someone needs to do this until the next major inspection" to "holy cow stop ALL traffic NOW".

[1] https://www.stbapa.bayern.de/service/medien/meldungen/2023/2...

[2] https://www.fba.bund.de/DE/Meldungen/20230201_Tunneluntersuc...

[3] https://www.merkur.de/lokales/muenchen/baustellen-besuch-sta...

[4] https://www.autobahn.de/aktuelles/aktuell/tunnelwartung-im-b...

t435623• 2 months ago

Software is super complex and cheap to update. Engineering like this, however difficult, is not that complex and it's very expensive and difficult to update.

We take advantage of the situation. If we invented some way of e.g. "growing" structures that turned out to be much cheaper we'd probably adapt our attitude to changing them.

lukan7• 2 months ago

When you say Engineering is not that complex, have you taken into account corrosive sea water, pressure, currents, what it means to make repairs and maintainance down there etc? It is difficult, because it deals with a very complex world full of physics, chemistry and even biology in a way that does not allow errors.

Towaway694• 2 months ago

Software isn't inherently complex, it becomes complex. Because it is iterative. Because we keep making demands of it that weren't planned.

Imagining building a bridge and then in the middle someone comes along and says it should also be a tunnel. I think therein lies a main difference to engineering and software engineering: planning and sticking to a plan.

Another thing are incentives: real engineering has real incentives to do it right, else you will get sued - by the families of those that died. Software engineering does not have this incentive to get it right.

tokai4• 2 months ago

The relationship is that software developers co-opted the term because it has excellent reputation and trust. In real life there is almost zero overlap in the how engineers and software developers work and develop their methods.

JHer• 2 months ago

I will keep recommending Hillel Wayne's crossover project whenever this "Software engineering vs 'real' engineering" discussion pops up.

https://www.hillelwayne.com/tags/crossover-project/

I'm disappointed and jaded by the state of our craft like you. But I'm also very suspicious of claims that other disciplines are somehow these much more earnest, pristine, derived-from-first-principles things. It just doesn't fit my view of human nature.

lostdog• 2 months ago

Is real, physical engineering that much better?

Take the new sf bay bridge span. It leaked, and had to be fixed to prevent critical parts from corroding. https://www.sfgate.com/bayarea/article/Caltrans-was-warned-o...

Projects are consistently over budget, late, and shoddily done in the physical world too.

teekert• 2 months ago

Hmm, 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.

internet_points• 2 months ago

there must be some way to make the browser disable it?

TazeTSchnitzel3• 2 months ago

On 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• 2 months ago

See 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 :)

Skwid• 2 months ago

If you disable javascript it scrolls normally. There's also no text, or images, but you can scroll past all the pretty background colours

tocs3• 2 months ago

I 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.

TazeTSchnitzel3• 2 months ago

This 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• 2 months 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• 2 months ago

I 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-skonc...

mrlonglong• 2 months ago

There's even a website gambling on how late DB trains will be.

https://bahn.bet/

skrebbel• 2 months ago

If they had built a tunnel to Rostock, things would have been different…

That would’ve been an extremely long (and expensive) tunnel.

TazeTSchnitzel3• 2 months ago

Yes, and it would have required much more investment in rail upgrades in eastern Germany. I can understand why they didn't go for it.

ianburrell2• 2 months ago

The Rostock bridge was proposed and this tunnel selected instead.

My understanding is that the water farther east is shallower which makes bridge cheaper. But not enough to be chosen.

bobthepanda2• 2 months ago

To be fair, a future reasonable upgrade might be a high or higher speed line from Lübeck to the Hamburg-Berlin high speed line.

rbanffy3• 2 months ago

And 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• 2 months ago

Isn'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.

rbanffy3• 2 months ago

I 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• 2 months 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.

dredmorbius2• 2 months ago

Such proposals exist under the rubric "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.

rbanffy3• 2 months ago

That’d be awesome. What is the current tallest ship that could damage a bridge? You can count on someone eventually doing that.

Aardwolf• 2 months 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• 2 months 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• 2 months ago

how do you protect something like this from someone deciding to blow themselves up in the middle of the tunnel?

First tunnel element of the Fehmarnbelt Tunnel immersed

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