The world's longest submerged tunnel will connect Denmark to Germany

According to the government of Denmark, construction works on the longest immersed tunnel in the world that will link Denmark with Germany, will begin in early 2021.

The "Fehmarnbelt" underwater tunnel that will serve both as a rail and road passage, will connect the 2 countries through the Danish island of Lolland and the German harbor of Puttgarden. The total length of the facility will reach about 18 kilometers. 

Currently, people traveling from one side to the other have to take a ferry boat and make a minimum 45-minute route. However, when the tunnel is completed, the passage will be crossed using a train or a car in 7 or 10 minutes, respectively. “The Fehmarnbelt link will be a new gateway to Europe and a new gateway for future green transport solutions," Benny Engelbrecht, the Transport Minister of Denmark, stated.

The facility will not be similar to the Channel Tunnel, the famed project that connects France with England underwater. The Channel Tunnel was significantly larger but their main difference in that is was constructed under the seabed.

Instead, the new project will be established above the seafloor. In particular, the facility will be made of hollow sections made of concrete that will be assembled together in an underwater trench. Each tunnel section will weigh around 73,000 tons but, it will float underwater due to its hollowness. The concrete sections will be precast on land and will be transferred near the location where they will be immersed by tugboats.

The trench will be 16 meters deep and 60 meters wide. The excavation works will retrieve 19 million m³ of rock and sand material that will be utilized to establish natural areas both in Denmark and Germany. 

The project was initially announced 5 years ago with Denmark's government setting the completion date for 2024. However, according to current estimates, the tunnel will be operational by 2029. Construction works were expected to begin earlier (in 2020) but they were postponed due to the COVID-19 outburst that has devastated most of the engineering initiatives worldwide.

The total cost of the project is expected to reach $8 billion, according to 2015 estimates.

To learn more about the construction process that will be followed to achieve the stunning facility, watch the video below.