Real-Time Current Forecast for Tunnel Element Towing

Vladan Babovic
Danish Hydraulic Institute

The construction of the fixed link across Øresund — following the 1991 agreement between the Swedish and Danish governments — is now almost completed. The fixed link consists of a combined twin track railway and a four-lane motorway. The total link length will extend just under 16 km between Kastrup on the Danish coast and Lernacken on the Swedish coast. One of the elements of the link is an immersed 3510-meter long tunnel under the Drogden navigation channel.

The immersed part of the tunnel consists of 20 elements, each approximately 175 meter long, resulting in a total immersed tunnel length of 3510 m. The outer cross-sectional dimensions are 8.6 m by 38.8 m, enclosing two railway tubes, two motorway tubes, and a central escape and installation gallery. The elements are placed in a pre-dredged trench, and founded on bedding sand.

All 20 tunnel elements are fabricated in a purpose-built casting yard at the Nordhavn area of Copenhagen harbour. The transportation distance to the tunnel site is 20 km. The towing configuration is with two leading tugs and two assisting tugs, i.e. one at each corner of the element. Figure above indicates locations of casting yard, tunnel site and towing route. The total duration of a towing and element immersion is expected to last up to 36 hours.

The planning of the transportation and installation of tunnel elements requires a wealth of knowledge about the current conditions in Øresund. In order to assist in a planning of such a critical operation Danish Hydraulic Institute developed a real-time forecast system producing predictions of speed and direction of currents at the location called Nordre Røse (situated near tunnel site) as well as water levels at Nordre Røse and Dragør.