The first of the 89 elements for the Fehmarnbelt Tunnel is on its way to the immersion point off the coast near Rødbyhavn on the Danish island of Lolland.
The 217m-long and 73,500-tonne concrete element left the work harbour of the tunnel factory at 9pm yesterday. In preparation for the immersion, Femern Link Contractors added a further 4,500 tonnes of ballast concrete to ensure the element is heavy enough to sink to the seabed.
The journey to the future tunnel portal is just over 2km.
The tunnel element contains four tubes that will house the motorway and the railway. There is also a service tube for technical installations.
The element is being transported with the help of five tugboats and a vessel built specifically to immerse the element.
The tunnel element is sealed at both ends and filled with air. However, as the road traffic tubes are heavier than the railway tubes, the outer railway tube is fitted with temporary water chambers to ensure the element remains horizontal during immersion.
“This is a very complex manoeuvre, which has never been carried out on this scale before. The elements of the Fehmarnbelt tunnel are both wider, heavier and longer than those used to build the Øresund link, and we will be working in significantly deeper water,” said Lasse Vester, deputy contract director at Sund & Bælt.
The tunnel element will lie in an 18km-long trench on the seabed from Rødbyhavn to Puttgarden. Before immersion, a bedding layer of gravel has been laid in the tunnel trench to ensure that the element rests in the correct position.
“It is a major task with very little margin for error. We have to immerse an element that is as long as two football pitches, within just a few millimetres. That places great demands on the equipment and on our contractor, which is why they have been preparing for this task for a long time,” said Vester.
The transport of the element and the immersion itself are expected to take several days. Once the element has been connected to the tunnel portal, rocks and gravel will be placed along the sides of the element to keep it in position.
Construction of the 18km-long Fehmarnbelt Tunnel is one of Europe’s largest infrastructure projects.
Connecting Germany and Denmark, the tunnel will be the longest of its kind in the world. It will contain a two-lane motorway in each direction and two electrified railway tracks for high-speed trains. Travel time will be 10 minutes by car and seven minutes by train.
