The world's longest immersed rail/road tunnel is coming to a place near ... me

[SteamPower4ever]

This Thursday as part of my job I visited the construction site of the Fehmarnbelt Fixed Link, which - when completed - will be the world's longest immersed road and rail tunnel, linking Denmark and Germany. Currently under construction is the factory for the tunnel elements and the associated work harbour, and the scale of the construction site alone simply blows my mind.

The company building the tunnel is Femern A/S, which is a subsidiary of Sund & Bælt Holding, which is also the parent company for Storebælt A/S, which owns and operates the Storebælt Fixed Link where I work and which includes two bridges and a tunnel.

While I'm in operations of the sister company and thus not directly involved in the construction of the tunnel, we are indeed working with the design and construction teams to incorporate the lessons learned from years of operation and maintenance on the Storebælt link. A minor tweak of the design now can make life easier (and operations cheaper) decades down the line, for example by making sure that there are easy ways to replace large drain pumps, high voltage transformers and other items and systems that have shorter life spans than the tunnel itself.

A Youtube construction channel recently made a great video about the project, but what the video does not really mention is the connecting infrastructure works in Denmark, including the new high speed line out of Copenhagen and electrification and upgrading the rest of the line to Fehmarn to 200 km/h line speed. Part of the upgrade is a new bridge across the Storstrøm strait, replacing the ageing 3.5 km single-track bridge from 1937.

[Army-Gandydancer]

Very interesting to say the least. The Channel Tunnel was still under construction when I was stationed in Germany. The Channel Tunnel opened up in 1994 but I never got the chance to travel through it. I left Germany in Dec 94 but spent most of that year in the field training for the Bosnia peace keeping mission.

[el Gato Gordo]

That is fantastic! I worked on the 2nd Hampton Roads Bridge-Tunnel in 1976. It was built in sections, barged out to location and sunk into place. Sections were joined underwater as they were built. Rapid tidal flow through there complicated placement. I worked on mainline wiring to get power to the ventilator buildings.

That was only a two lane highway, since it was a 2nd parallel unit. I can only imagine how the difficulties expand exponentially on this new tunnel!

[Army-Gandydancer]

I'm sure it is difficult to place tunnel sections, especially with strong currents. I worked a little on one of the Lock and Damns on the Mississippi River back in 1989. That was bad enough trying to get concrete forms set just right with the river's current.

[SteamPower4ever]

Fortunately there are no strong currents at the entrance to the Baltic Sea where the tunnel is being built, but the ground below varies significantly from very hard (almost as concrete) at the Danish coast to fairly soft at the German coast. But that is of course being dealt with by the construction teams.

The tunnel is currently scheduled to open for traffic in 2029, which - give or take a few years - is when I retire, so along the way I'll be surprised if I'm not dragged into the project more than I am now

[NtheBasement]

Sound cool except for the 100 euro toll. How much is the Chunnel toll?

[Scotian_Huntress]

See: https://www.eurotunnel.com/uk/tickets-and-fares/
https://www.eurotunnel.com/fr/billets-et-tarifs/
It appears to be 98 Euros one way per vehicle?

[SteamPower4ever]

Sound cool except for the 100 euro toll.

It's pretty much the same price as the ferry today.

[el Gato Gordo]

I didn't catch how long the tunnel will be. I wonder how they will ventilate the automobile exhaust gasses?

[Jugtown Modeler]

It is hard to imagine the engineering that has to go into these massive projects. Even one aspect, ventilation, must be an enormous task.
The Hvalfjörður Tunnel in Iceland is only 5,770 meters /18,930 ft long, not an immersion tunnel, but has been criticized for poor ventilation and lighting. I believe I read it was done very cost effectively and paid its cost to build off in something like 10 years. (don't quote me) But may account for some of the safety issues around it.

[Heiko]

I didn't catch how long the tunnel will be. I wonder how they will ventilate the automobile exhaust gasses?

It's going to be 18km / 11 miles: https://en.wikipedia.org/wiki/Fehmarn_Belt_fixed_link

Ventilation is an issue. One of the more complex ones, along with firefighting and evacuation concepts, for sure.

A friend of mine - volunteering for the German civil protection agency THW - was posted to a much shorter, 1.6km / 1 mile tunnel a couple of years ago to supervise the emergency generators. Basically all he did was sit there, watch the generators to make sure they were ready to start in case of a power loss and complain about bad cellular data coverage in the area but that kind of tells you how important uninterrupted ventilation is for that kind of tunnels.

Heiko