dcsimg Immersed tunnels - Ramboll UK Limited

Immersed tunnels


Immersed tunnels, or tubes, are used most often to cross water. Ramboll’s innovations here set new standards for modern tunnel design. We have designed two of the world’s three longest immersed tunnels. Our multidisciplinary team of tunnel engineers excels in structural and ventilation design, and state-of-the-art safety and security features.

The world's longest immersed tunnel

In 2009, Ramboll (as lead partner in a joint venture) won the design competition for the forthcoming 18km immersed tunnel across Fehmarnbelt between Germany and Denmark. The road and rail tunnel is a record-breaking structure, more than three times as long as any existing immersed tunnel. It saves drivers a 45 minute ferry crossing and train passengers a 160km detour.

Fehmarnbelt Fixed Link tunnel is designed in accordance with EU Directive 2004/54/EC on road tunnel safety, and incorporates state-of-the-art safety and security features. Functionality and user comfort are maximised by a pioneering longitudinal ventilation system, while varied lighting keeps drivers alert.

In the Fehmarnbelt Tunnel Blog, senior project director Susanne Kalmar Pedersen describes the ongoing work.

Other flagship immersed tunnel projects

Ramboll led an international joint venture in designing the 4km tunnel between Copenhagen and the artificial island of Peberholm as part of The Øresund Link between Denmark and Sweden. It opened in 2000, carrying a dual-track railway and a four-lane motorway, and was then the longest immersed tunnel in the world.

We have had key roles in the design and construction of the twin tubes of the Preveza-Aktio road tunnel in Greece, and the metro tunnel under the Vlatava River in Prague.

We also undertook major repairs to the 1969 Limfjorden highway tunnel in Denmark. Work included longitudinal post-tensioning of the tunnel structure, injection of cracks and joints, renovation of the interior surfaces and a fire safety analysis.




External information about immersed tunnels

Logo of Femern AS
Femern Belt

Visit Femern Sund Bælt's website to read more background about the project and see their many videos and visualisations.

Øresundsbron AS logo

Øresundsbron AS is the company for the combined immersed tunnel and bridge crossing between Denmark and Sweden.



Stephen Whitham
Stephen Whitham
Head of Department, Tunnels
T+45 51615202
Richard Miller. Ramboll
Richard Miller
Technical Director, Ground Engineering
T+44 20 7631 5291