A pontoon the size of a football pitch has arrived at Rødbyhavn harbour in Lolland, Denmark for the next stage in sinking the largest tunnel of its kind in the world.
Built at the Polish shipyard of Crist, Gdynia in Polen, the immersion pontoon is actually two vessels that can be used individually or as one piece.
Ivy 1 and Ivy 2 will support the 217m-long elements of the Fehmarnbelt Tunnel from the harbour to their point of immersion between Denmark and Germany, where they will form an 18km subsea tunnel connecting the two countries.
“”The Immersion Pontoon has two main functions: to support the elements and to control the immersion process. The vessel contains winches with over 200 km of steel wire and a control room from where the immersion process will be managed,” said Baris Nacar, Construction Marine Manager for Femern, the contractors building the tunnel.
“Ivy 1 and Ivy 2 will support opposite ends of each standard element. However, the special elements, which are significantly shorter, will be supported by the two vessels coupled together.
“It will require a steady hand and some highly advanced equipment to immerse the tunnel elements with the precision we require. Our Immersion Pontoon, therefore, has been specially built for this purpose.”
In total, 79 tunnel elements, each 217m x 42m, and nine metres high, are being produced from nine castings or segments, each 24m long. Another 10 elements will be cast in different sizes.
Once sunk, the elements will be fitted together with millimetre precision, the water pumped out and a partial vacuum lock them together.
A layer of protective stone will cover them, in turn being layered naturally with gravel and sand.
The tunnel will start and finish in Lolland in Denmark and Puttgarden in Germany. As well as containing by road, a railway track will accommodate a 200km/h train that will connect Hamburg with Copenhagen in less than three hours.
The tunnel is due to be completed in 2029.
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