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The first element for the Fehmarnbelt tunnel is positioned in front of the Danish tunnel portal (Sund & B\u00e6lt)<\/p>\nThe first element for the Fehmarnbelt tunnel is positioned in front of the Danish tunnel portal (Sund & B\u00e6lt)<\/p>\n
\nThis week saw the sinking of the first concrete section of the 18-km-long Fehmarnbelt tunnel linking Germany and Denmark, which claims to be the world\u2019s longest immersed combined road and rail tunnel.\n<\/p>\n
The precast section, 217m long and weighing 73,500 tonnes, contains two road tubes, two rail tubes, and a service tunnel.<\/p>\n
The days-long operation starting 4 May saw five tugboats pull the section just over 2km from the fabrication hall into place for submersion at the future tunnel portal on the Danish island of Lolland.<\/p>\n
The section was attached to a vessel built to immerse the element down onto the seabed.<\/p>\n
4,500 tonnes of ballast concrete were added to the section to make it sink into place in an 18km-long trench prepared on the seabed with a layer of gravel laid to ensure it rests in the correct position.<\/p>\n
The section is sealed at both ends and filled with air except for the narrower and therefore lighter railway tubes, the outer one of which was filled with temporary water chambers to make the tunnel fall evenly into the trench.<\/p>\n
\u201cIt is a major task with very little margin for error,\u201d said<\/a> Lasse Vester, a deputy contract director at the project\u2019s developer, state-run Sund & B\u00e6lt.<\/p>\n \u201cWe have to immerse an element that is as long as two football pitches, within just a few millimetres.<\/p>\n \u201cThat places great demands on the equipment and on our contractor, which is why they have been preparing for this task for a long time.\u201d<\/p>\n