Tailor-made sealing systems for the Fehmarnbelt immersed tunnel

As seen on Femern Magazine

At 50 meters below the water's surface, the upcoming Fehmarnbelt immersed tunnel will span 18 kilometres between Denmark and Germany. As work gets underway, this massive infrastructure project brings about significant challenges, especially when it comes to the tunnel sections.

Trelleborg Marine & Infrastructure has an extensive track record in immersed tunnel projects worldwide. However, the scale of the Fehmarnbelt project and the safety requirements were enormous, presenting unique challenges in creating the appropriate water stops to seal the tunnel elements. As part of the design process, the team produced 89 Gina gaskets and 89 Omega seals to maintain the tunnel's integrity and prevent the movement of the elements on the partially exposed ground.

"Each project comes with its own set of challenges. When it comes to the Fehmarnbelt tunnel, for instance, the type of l ground condition and the sea depth play crucial roles. Typically, tunnels constructed on loamy clay are more susceptible to soil movement and displacement, which can lead to leaks. Our tailor-made water stops, portals, ramps, Gina gaskets, and Omega seals are specifically designed to seal deep joints between tunnel elements. The project required the production of the largest-ever Gina seals for submerged tunnels, capable of withstanding water pressure at the deepest point and expanding or contracting according to changing weather conditions.," explains Nicas van den Brink, Design Engineer at Trelleborg Marine & Infrastructure.

Global pipeline of large-scale infrastructure projects

Trelleborg Marine & Infrastructure is currently involved in several other large-scale projects around the world. One notable example is China, where immersed tunnels with similar tunnel elements are in the planning phase.

With its magnitude, the Fehmarnbelt tunnel is Trelleborg Marine & Infrastructure's most significant project to date, requiring innovative solutions.

"Having been involved in over 60 successful tunnel projects worldwide, Trelleborg was the clear choice as a partner for the Fehmarnbelt project. We take pride in our impeccable track record and are honored to contribute to the Fehmarnbelt tunnel, a project that has been in the design phase for 10-15 years to ensure the best solutions," says Rene Fredriks, Managing Director of Infrastructure Solutions at Trelleborg.

"Our waterstops for the elements, portals, ramps, as well as Gina gaskets and Omega seals, are tailor-made for the deep joints connecting the tunnel elements," adds Nicas van den Brink, Design Engineer at Trelleborg Marine & Infrastructure.

New patented system saves time
A project like Femern entails various aspects. For instance, Trelleborg Marine & Infrastructure has established two production facilities to ensure continuous production in case of any issues. This continuity and flexibility help maintain the project's schedule, as highlighted by Nicas van den Brink: "A project of this size, with numerous new solutions in play, comes with inherent risks. To address this, we have developed and patented a new waterstop featuring an interlocking system that accommodates the dynamic movements of the structure and fills any cracks. It is similar to a plug-and-play solution, which ensures project efficiency and saves time."