Fehmarn: longest immersed tunnel
The Fehmarnbelt tunnel is an 18-kilometre long immersed tunnel located 40 meters beneath the Baltic Sea that connects the Danish island of Lolland to the German island Fehmarn. It will be the world’s largest immersed tunnel and includes a two-track railroad and a four-track motorway. To date, it is the largest infrastructure project in Denmark, with a total budget of over € 7 billion.
The connection is important for Europe’s future transport network. By connecting Scandinavia with Central Europe, the belt enables a faster journey across East Denmark to Germany by taking seven minutes by train and 10 minutes by car. This shortcut saves travellers 160 kilometres. Additionally, it enables the transport freight industry to save both time and CO2 emissions, while freeing up road capacity by moving from trucks to environmentally friendly electric trains.
Ramboll has been an advisor to the client, Femarn A/S since 2009 within the Ramboll-Arup-TEC Joint Venture partnership. We are delivering the designs and plans for the tunnel and a wide variety of services such as consultancy in competitive dialogues processes and bud evaluations, support of planning of approval processes on the German side delivering technical support, review design and conducting construction assurance. Furthermore, we are providing consultancy on the sustainability strategy covering environment and social sustainability priorities within the construction and operation phases
This immersed tunnel solution challenges existing tunnel building standards, and will set a world record.
The Fehmarn Belt Fixed Link is five times as long as the Øresund Tunnel, and three times as long as the Transbay Tube in San Francisco, the longest immersed tunnel in the world today.
Constructing an 18-kilometre immersed tunnel itself requires meticulous design and planning. Our experts within the Ramboll-Arup-TEC Joint Venture have set the foundation for the project, including requirements for the basic geometry of the tunnel and its elements, the precise location, and prepared the technical specifications. Now, contractors will prepare the detailed design of the tunnel, while Ramboll-Arup-TEC Joint Venture assists the owner in reviewing the contractors’ designs.
Planning this massive project includes erecting a large-scale harbour to facilitate the delivery of casting materials. Also, a tunnel factory with six productions lines was built to cast 79 standard elements that will construct the tunnel. Each element is 217 meters long and weighs 73,5000 tons. Another 10 special elements were created which are shorter but wider.
After the tunnel segments are cast and assembled within millimetres of accuracy, they are pushed from the factory into a dry dock, which will be flooded. The elements are closed with waterproof bulkheads at the ends to contain air. This is how they can float.
Once in place below the seabed, the interiors covering ballast, road surface, technical, and mechanical installations will be put in place. This includes a pioneering longitudinal ventilation system and state-of-the-art safety and security features.
When completed, it will be as safe as a regular motorway or railway section on land.
All traffic types will take place in separate paths to minimize the risk of traffic accidents. A computer-controlled traffic control system and a 24-hour manned control centre will also be installed. In addition, there will be traffic information on FM radio, signage for road users, and varying architectural lighting to help maintain drivers’ concentration.
In addition to pushing innovative design solutions, Femern A/S has a strong focus on demonstrating social and environmental responsibility in the construction and operation phases.
Currently the Ramboll-Arup-TEC Joint Venture is assisting Femern A/S with strategy development, implementation, analysis, and impact assessments within three strategic sustainability priorities:
- Educating the next generation of the vocational workforce through apprenticeships and training. Femern A/S has committed to offering at least 500 internships in total for all relevant tenders and contracts covering the project.
- Minimising the project’s climate impact and becoming CO2 neutral during operation.
- Implementing one of Europe's safest construction sites by developing a strong safety culture for all working on the project. The labour demand in the construction phase alone is estimated to be up to 20,000 person-years in direct effects, with the strongest demand in 2024-2027.