The long-planned Fehmarn Belt Fixed Link between Denmark and Germany moved one step closer to reality this month.
The tunnel’s construction plan is also pretty striking, even in the post-Channel Tunnel era. As the above video shows, it will not be excavated below ground, but prefabricated and immersed in a trench dredged from the seabed, then covered over. The Baltic is relatively shallow in the Fehmarn Belt, making this method cheaper than either a deep tunnel or a bridge. The tunnel will actually be constructed on land on the Danish Coast, in 710 foot long sections that will themselves be subdivided into two rail tunnels, two three-lane highways and a service tunnel running between them. These sections will be sealed and floated out to the trench, where ballast tanks placed on top of them will be filled with water, forcing them down into the cavity. The trenches will then be filled with gravel and topped with stone.
watch the video: https://www.youtube.com/watch?v=9Cb6CRJwixw