The Revolution Blog

Invisible landmark or world’s largest immersed tunnel?

Tuesday, Oct 25, 2022

We’ve written a lot about how Hamilton products are supporting Tesla’s Hyperloop One tunnel, as well as the innovations happening with other types of boring tunnels. But this latest feat of engineering is pretty bananas.

It’s the world’s longest immersed tunnel, and it’s massive—at 11.1 miles long and snaking up to 40 meters beneath the Baltic Sea. It’s called the Fehmarnbelt Tunnel, and when it’s completed in 2029 it will link Denmark and Germany, providing the fastest route known to man between Scandinavia and Central Europe. By definition, an immersed tunnel is composed of tunnel elements built elsewhere and then floated and flowed to the right alignment in the water to be sunk into place and linked together.

It’ll take 360,000 tons of steel and 3 million cubic meters of concrete to bring Fehmarnbelt to life. This is one of Europe’s largest infrastructure projects—and one of the continent’s largest construction sites, too, with continuous casting 24/7. Unlike the Channel Tunnel, which was made using a boring machine to link England and France, Fehmarnbelt is being built by immersing pre-built tunnel sections that are cast and assembled section-by-section on land—then transported underwater. This incredibly ambitious project will be assembled from 87 sections that are incrementally caste over a skeleton of reinforcing steel in large casting molds. Watch this video to see the full process of how the tunnel is being built.

The finished tunnel will feature a number of state-of-the-art safety features, with an intelligent ventilation system in case of heavy traffic or fire, as well as emergency exits every 110 meters. The design also includes a crash barrier and emergency lanes.

Now all it needs is a gas station at the halfway mark and maybe a nice panoramic of fish for the kiddies.

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