The Fehmarnsund Tunnel is a 1.7km long immersed tunnel connecting the German mainland to the island of Fehmarn. The new crossing will carry a dual two-lane highway and twin high-speed rail lines, increasing the capacity of the existing crossing in anticipation of the completion of the Fehmarnbelt Fixed Link that will connect Germany and Denmark.
The German railway infrastructure company, Deutsche Bahn Netz AG, commissioned Ramboll to carry out a study of the immersed tunnel option, one of four parallel studies that also considered bridge refurbishment, replacement bridge, and bored tunnel options.
The immersed tunnel study included a concept design for:
- Immersed tunnel
- Tunnel portals, cut and cover and ramp structures
- Tunnel equipment
- Service buildings
- Road and rail alignment
- Highway works
The concept design included the development of methodologies for the construction of the tunnel structures, and in particular the temporary works associated with the precasting, transportation and immersion of the tunnel elements.
Ramboll were also responsible for the design of the service buildings to accommodate the technical rooms required for tunnel operation, including dedicated facilities for highway and railway maintenance. Ramboll proposed a largely subterranean facility to minimise visual impact.
The client selected the immersed tunnel as the preferred solution ahead of the bored tunnel and bridge options on the grounds of cost and the environmental benefits.