loadtest
Three tunnel elements have already been immersed in the tunnel trench in the Fehmarnbelt. The specialist vessel IVY is now berthed in the work harbour at Rødbyhavn with the fourth element secured in place. Once it has been immersed, the first approximately 900 metres of the 18-kilometre tunnel between Denmark and Germany will be in position.
The fourth element was used in a crucial test demonstrating that IVY can handle the next, fifth element, which is the tunnel’s first special element. It is shorter than the standard elements but has a basement containing technical installations for the tunnel.
At 39 metres long, 42 metres wide and 13 metres high, the special element is equivalent in size to a four-storey building, explains Lasse Vester, Deputy Contract Director at Sund & Bælt.
“The first special element is the size of a multi-storey building and must be positioned at a depth of more than 20 metres. Immersing such a large structure is a demanding operation, which is why it was necessary to test IVY thoroughly before deploying the vessel,” says Lasse Vester.
The Fehmarnbelt tunnel consists of 79 standard elements, each 217 metres long, and ten shorter special elements with a basement. The special elements are positioned at intervals of approximately two kilometres. Among other things, their basements house the tunnel’s technical installations, while at road level there is space for a service vehicle to stop without obstructing motorway traffic.
The load test was carried out using the current fourth standard element, which IVY holds securely at both ends. The special element's basement level requires it to ride higher in the water during transport. When the element is lifted further out of the water, buoyancy decreases and the load on IVY increases. The test simulated this additional load.
During the test, the fourth element was loaded with an additional 1,600 tonnes. The weight was distributed between large water bags on top of the element and tanks inside it. To pass the test, IVY had to be able to lift the element to the same height required when transporting the special element.
Following the successful test, the water bags are now being removed, and preparations for immersing the fourth element can continue.
“The test was a rehearsal for a highly complex technical operation. We now know that IVY can handle the additional load and immerse the special element safely and precisely on the seabed,” says Lasse Vester.