Contractor tests special vessel for immersion of tunnel elements

At present, the contractor consortium Femern Link Contractors (FLC) is testing the special vessel that will immerse the tunnel elements for the Fehmarnbelt tunnel. Over the weekend,  the unique immersion pontoon IVY 1 & 2 carried out the first test of connecting the vessel to a completed tunnel element.

The immersion pontoons are currently located in the large Danish work harbour on Lolland, with the first tunnel element secured between the two units. The initial phase of testing has already been successfully completed and includes, among other things, confirming that all functions operate correctly – both when IVY 1 & 2 are operated separately holding a standard element secured in between, and when they are operated as a combined vessel. 

During the final phase of testing, additional weight will be added to the secured element, corresponding to the amount of ballast concrete required to weigh the element down. IVY will then lower and raise the element for test purposes in the work harbour. The contractor consortium FLC expects this phase of testing to be completed during March.

“IVY 1 & 2 is a completely unique vessel, built specifically for the tunnel elements used for the Fehmarnbelt tunnel. It has taken longer than expected to complete and test the vessel. FLC is now close to reaching the finish line, enabling the vessel to be approved to play the key role in the immersion of the tunnel’s many elements. We expect the first element to be immersed and connected to the tunnel portal at Rødbyhavn later this spring,” says Lasse Vester, Deputy Con-tract Director at Sund & Bælt.

Once the vessel has been approved by the Danish maritime authority, IVY will bring the tunnel element to the quay in the Danish work harbour, where additional concrete will be pumped into the element. This will make the element heavy enough to sink to the seabed. From that moment on, it is kept afloat solely by the buoyancy of the two immersion pontoons. IVY 1 & 2 will then transport the element to the tunnel trench and immerse it in a controlled manoeuvre with millimetre precision.

About the Fehmarnbelt tunnel and IVY 1 & 2

• The Fehmarnbelt tunnel is 18 kilometres long and consists of 79 standard elements and 10 special special elements featuring a basement level for the tunnel’s technical systems.
• Before a standard element can be transported and immersed, each end is connected respectively to IVY 1 and IVY 2, which keep the element afloat.
• When a special element is to be transported, IVY 1 & 2 are combined into a single vessel to carry out the immersion.
• IVY 1 & 2 are equipped with a total of 23 kilometres of steel wire distributed across 66 winches, which are used to immerse the element into the tunnel trench at depths of up to 40 metres, with millimetre precision.