Doka shapes Fehmarnbelt Tunnel portals

The Fehmarnbelt Fixed Link, connecting Denmark and Germany under the Baltic Sea, is set to become the world’s longest immersed tunnel when it opens in 2029. At 18 kilometres long, this engineering feat will reduce travel time and provide a green transport corridor between Scandinavia and mainland Europe.

Doka, a global formwork expert, is integral to the construction of the tunnel portals and ramps, which will serve a four-lane motorway and double-track railway. The portals, built using a segmented cut-and-cover method, involve assembling 20-metre-long sections with high-precision formwork solutions.

The project is being delivered by Femern Link Contractors (FLC), a joint venture comprising VINCI Construction Grands Projets (France), Aarsleff (Denmark), Max Bögl Stiftung & Co. KG (Germany), BAM Infra (Netherlands), BAM International (Netherlands), Wayss & Freytag Ingenieurbau (Germany), Solétanche-Bachy International (France), CFE (Belgium), and Dredging International NV (Belgium).

Doka is managing every stage of the formwork process, from design to on-site assembly. The work includes:

• Planning the 3D-designed formwork concept for five tunnel tubes, including a narrow 2-metre-wide maintenance gallery.
• Supplying five heavy-duty tunnel formwork travellers based on the SL-1 system, including a monoleg traveller for confined spaces.
• Pre-assembling formwork units with shear keys for interlocking segments, ensuring safety and alignment.
• Developing custom solutions for ventilation niches and transitions between land and water, integrating a steel frame with high precision to meet tight tolerances.

The BIM-supported process ensures efficient planning and execution, minimising errors and improving construction safety. Andreas Zitzenbacher, head of large-scale project management at Doka, highlights the importance of collaboration: "For a project of this scale, which crosses national borders, professional project management is crucial for a solution-oriented and constructive collaboration. This is the only way we can support our customers as a reliable partner and successfully achieve our common goal - Northern Europe's largest infrastructure project."

Concrete at the core

Doka’s on-site teams in Puttgarden and Rødbyhavn oversee the handling of 1,400 tonnes of formwork material. Concrete is poured in stages, starting with the base slab for the tunnel tubes and maintenance gallery, followed by the advancing walls and roof slabs.

Doka pre-assembly services ensure customised formwork units are delivered ready to use, reducing time on-site. Specialised solutions for ventilation niches and steel integration demonstrate Doka’s commitment to precision and safety.

The Fehmarnbelt Fixed Link is expected to streamline travel, reduce CO₂ emissions, and support greener transport in Europe.