Longest Underwater Tube Tunnel in the World

A new 18km long rail and road tunnel is currently under construction to connect Germany and Denmark, which will significantly reduce travel time from 45 minutes to just 7-10 minutes. The Fehmarnbelt tunnel, built by Femern A/S, Rambøll, Arup, and TEC, is set to be the world’s longest and deepest submerged tube tunnel with combined rail and road capabilities. Once completed, this tunnel will link the town of Rødbyhavn in Denmark to the island of Fehmarn in Germany, providing a more efficient route between Scandinavia and the rest of Europe.

The construction of the Fehmarnbelt tunnel has been a massive undertaking, requiring 360,000 tons of reinforcing bars, nearly 50 times the weight of the Eiffel Tower’s metal structure. The construction site on the Danish side covers an area as large as 373 football fields, and the dredging operation for the 18 km long tunnel involves up to 70 ships. In total, about 12 million m3 of soil has been excavated from the seabed.

The tunnel consists of 79 standard sections and 10 special sections, each weighing around 73,000 tons. The standard sections are 217m long, 42m wide, and 10m high, while the special sections are smaller but slightly wider and taller. These tunnel sections are prefabricated on land, transported by barge, and then submerged and sealed on the seabed at depths of up to 40m.

With a construction cost of approximately $1.2 billion, the Fehmarnbelt tunnel is expected to be completed by 2029 and operate for at least 120 years. Once operational, passengers will benefit from significantly reduced travel times and a more efficient transportation link between Denmark and Germany.