Immersed tunnels


Stephen Whitham

Stephen Whitham

Global Division Unit Manager, Tunnels
T: +45 51615202
Richard Miller. Ramboll

Richard Miller

Director Ground Engineering & Tunnelling
T: +44 7436 269130

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

Femern Belt

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


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


Engineers discussing the Fehmarnbelt tunnel

Fehmarn: The world's longest road/rail tunnel

In the future Scandinavia and the rest of Europe will be connected by the world's longest road and rail tunnel.

Øresund bridge

The Øresund Link

The Øresund Link connects the Danish capital Copenhagen with the city of Malmö in southern Sweden by a four lane motorway and a two track electrified railway for high speed (200 km/h) passenger services as well as freight trains.


The population in Western part of Sweden is growing and capacity problems on the railways in and around Gothenburg are increasing.

Maintenance of the Limfjord Immersed Road Tunnel

Ramboll was chosen to undertake overall repairs on the Limfjorden immersed highway tunnel, which has a total length of 550 meters.

Vlatava River Crossing

The tunnel consists of two tubes app. 6.5m x 6.5m each with a total length of app. 170m. A new technology for immersion, sliding and pulling under water has been invented for this project.

Päijänne Water Tunnel

Refurbishment of Päijänne Water Tunnel

Supervision of the refurbishment of the worlds’ longest rock tunnel that carries water to the capital of Finland. Finland’s Päijänne Water Tunnel (constructed in 1972) is the world’s longest continuous rock tunnel and provides Helsinki and surrounding cities with pure water from Lake Päijänne in central Finland.

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Ramboll UK Limited. Registered in England & Wales. Company registration no. 03659970. Registered office: 240 Blackfriars Road, London SE1 8NW

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