A 21,000-ton concrete element has just emerged from the casting area at the tunnel factory near Rødbyhavn. The element is the first of a total of 10 special elements, which are key components in the construction of the Fehmarn Belt Tunnel, according to Femern A/S.
The element consists of two levels, with the lower level serving as a basement that will house the tunnel's extensive electrical installations. Above, on the "ground floor" of the element, are the separated tunnels for rail and road traffic.
In addition to the basement, the element is equipped with a lay-by in the motorway tunnel, where technical personnel can park without disrupting the rest of the traffic and easily access the basement. This allows for smoother operations and enhances the safety within the tunnel.
A Unique Solution
The use of special elements is the single largest innovation in the Fehmarn Belt Tunnel, which otherwise largely follows the model of the Øresund Tunnel.
“The special element is a unique solution that consolidates the tunnel’s technical installations into 10 hubs, rather than spreading them along the entire 18 kilometers of the tunnel. This reduces both the amount of concrete needed for casting and the excavation of the seabed. At the same time, the solution enables efficient traffic flow and provides safe access for staff who will maintain the tunnel,” says Jens Ole Kaslund, Technical Director at Femern A/S, project developer and subsidiary, of the Danish state-owned company Sund & Bælt.
Over a Year of Casting Process
The special element is 39 meters long and approximately 13 meters high, equivalent to a 4-story building. In addition to the 10 special elements, the tunnel contractor, Femern Link Contractors (FLC), will cast 79 so-called standard elements, each of which is 217 meters long and weighs 73,500 tons.
The special elements are cast almost like a house in three stages: first, the basement is cast, then the walls, and finally, the rooftop. The casting process for the first special element has been ongoing for just over a year, during which valuable experience has been gained for the work on the subsequent elements. Special element number two is already in the process of having its basement cast. These elements can be cast over a longer period since only 10 are needed, each placed approximately every two kilometers along the total 18 kilometers of the tunnel.
“We are very pleased that the casting of the first special element has been successfully completed. These days, we allow ourselves a moment of celebration, but we know that there is still a long way to go, and we have great respect for the complex work that still lies ahead,” says Nick Geurts, Division Manager at FLC, responsible for the production of the special elements.
Five Standard Elements Completed
On the tunnel factory's five other production lines, FLC has completed the first five standard elements and is working on the next ones in line.
The first special element is expected to be lowered into place off the Danish coast during 2025.
The construction of the Fehmarn Belt Tunnel is the largest infrastructure project in Denmark's history and the largest construction site in Northern Europe. The 18-kilometer-long tunnel will be the longest immersed tunnel in the world. Once completed, it will be possible to cross the Fehmarn Belt in 7 minutes by train and 10 minutes by car.
Facts about the Special Element
- Number: 10
- Length: 39 meters
- Width: 47 meters
- Height: 13 meters
- Weight: 21,000 tons