N57 Aqueduct - Middelburg

The N57 is the main road on Walcheren (Zeeland) which needs reconstruction, a new part of this road is a crossing with a channel. Crossing the channel and disturbing the traffic on this channel as little as possible, was achievable by using an immersed element.

Combination Strukton-Rasenberg
The Netherlands
N57 - TE ready for immersion
N57 - pull down principle
N57 - survey tower
N57 - P1040569
N57 - inside TE without Ballasttanks
N57 - finished overview


For Strukton Immerson Projects the project consists of 1 tunnel element. The element will be built at the south side of the channel, in the cut-and-cover construction site, which afterwards will function as an approach ramp. When the element and the abutment on the north side are finished the inundation of the construction site will start. When the element is floating, an additional concrete ballast is added on the deck of the element, to reach the desired freeboard.

When the desired freeboard is reached and the immersion tools are in place the element is ready to go. The element will be towed from south to north by a winch configuration at the north side and extra winch at the south side stop the element when it reached its immersion location.

For the immersion of the element we are using a new technique which has never been done before by the immersion of tunnels. Instead of creating an overweight by filling tanks with ballast water and lowering the element by winches to its desired location, we do the opposite. We are going to pull the entire element to the desired location! We do this by holding the element in horizontal direction on a fixed location and  we pull it downwards with winches in a special winch configuration on the primary an secondary side of the element.

When this is done, a sand flow will be added underneath the element. To give the element an overweight a ballast layer is added on the deck of the element. Now the winches can be disengaged and the element is ready for its finishing touch.