Femernbelt Fixed Link Immersed Tunnel, between Rødbyhavn and Puttgarden, Denmark/Germany

The ferry between Rødbyhavn and Puttgarden will be replaced by a tunnel with a railway and motorway for in order to shorten journey time between Copenhagen, Denmark and Hamburg, Germany and to create a greener corridor. The tunnel consists of a four-lane motorway in two tubes and two railway tracks in single tubes. The world’s longest immersed tunnel (17,6 km) is being constructed between Rødbyhavn on Lolland (Denmark) and the German island of Fehmarn, 40 metres beneath the Baltic Sea.  

Casting the tunnel elements

The large-scale production plant for casting and shipping out the tunnel elements is being built. In the factory, a standard element will be produced approximately every second week for some three and a half years. Production of 79 standard and 10 special elements will be required in total. Each special element will include a 'basement' area for technology. This will make the construction process and maintenance of the finished tunnel easier. The tunnel elements are manufactured using industrial series production, which makes the construction process considerably more efficient.  

Laser focus on quality

The elements will be cast step-by-step in segments of approximately 24 metres in the factory. Nine segments comprise one standard element and the whole process takes about nine weeks. A high degree of uniformity and quality in the casting can be ensured because it takes place inside climate-controlled halls. This is important as the Fehmernbelt tunnel is designed to operate for at least 120 years.

Immersing and coupling the elements together

When an element is ready for shipment, it gets waterproof bulkheads fitted at both ends and is towed into place using tugs. The elements are then lowered to the seabed with high precision and are carefully coupled together. There is a sealed space between the bulkheads so that huge external pressure pushes them together when the water is pumped out. This ensures a completely waterproof connection. 

Our scope includes extensive temporary works in order to produce 79 tunnel elements and 10 specials:  

• harbor works required for the import of materials for construction as well as for the float-out and immersion of the constructed tunnel elements
• two large heavy compensated immersion pontoons
• the bulk heads
• access shafts
• steel rolling gates to close the factory docks
• design of the dikes
• skidding beams

We also support the FLC consortium with coordination of various permanent works design packages.