The special vessel that will immerse the large elements of the €7.1bn (£6.1bn) Fehmarnbelt tunnel linking Denmark and Germany has been approved by the Danish Maritime Authority.
The project had been under “considerable pressure” due to significant delays in bringing the immersion vessels to site.
Femern Link Contractors (FLC) is now preparing to immerse the first tunnel element into the dredged tunnel trench off Lolland’s coast this spring.
Special vessel Ivy is comprised of two distinct units, Ivy 1 and Ivy 2. For the 39m long special elements, Ivy 1 and 2 will be joined to form a single vessel that will facilitate the immersion process.
Before the transportation and immersion of a 217m standard long tunnel element, each end will be attached to the two units to provide buoyancy.
Between them, Ivy 1 and 2 are equipped with 23km of steel wire spread over 66 winches. This enables them to submerge tunnel elements to depths of up to 40m.
FLC has already completed the preparation of the first part of the tunnel trench. This includes laying an even gravel foundation to ensure the bottom of the trench is completely level.
Ivy 1 and 2 were brought to the jetty this month with the tunnel element secured between them. Ballast concrete will be added to the element to ensure it’s heavy enough to sink. The vessel units will then transport the element to the trench and immerse it.
Lasse Vester, deputy contract director at Sund & Bælt, the owner of Fehmarnbelt tunnel, said: “Ivy is a unique vessel developed exclusively for the construction of the Fehmarnbelt tunnel.
“Its task is complex, so a long sequence of tests had been necessary to ensure that it meets the high technical and safety requirements set by both us and the authorities.
“Ivy has now passed all tests, and we look forward to FLC beginning the immersion of the first tunnel element later this spring. It will be a challenging operation, which we have to repeat a further 88 times until all elements are in place.”
The construction of the 18km long immersed tunnel is one of Europe’s largest infrastructure projects.
Fermern, a specially created subsidiary of Sund & Bælt, the Danish state-owned transport management firm overseeing the megaproject, said that construction has been delayed for at least two years.
The immersed tunnel is being designed and constructed by FLC – a consortium made up of Vinci, Aarsleff, Wayss & Freytag, Max Bögl, CFE, Solétanche Bachy, Bam Infra, Bam International and Dredging International.
The tunnel will contain a two-lane motorway in each direction and two electrified railway tracks for high-speed trains. Cars will be able to cross countries in 10 minutes, while train journeys will take seven minutes.