MARINE CIVILS

Afsluitdijk reinforcement will use improved interlocking blocks

6 years ago

Plans to both strengthen and raise the height of the long Afsluitdijk across the Isselmeer in Holland have seen a contract awarded to a consortium that has started work writes Dag Pike.

X-BlocPlus has been developed for this project

The consortium, comprising the major construction companies Van Oord, BAM, and Rebel, has been contracted to complete the reinforcement work by 2023. Working under the title of Levvel, the construction consortium has successfully placed the first of the special designed blocks on the 32km long dam. In total the consortium will be placing 75,000 of these specially designed concrete blocks as part of a major reinforcement project to heighten the dam and to make it more resilient to cope with predicted rising sea levels and to withstand overtopping.

In addition to the placement of the reinforcing blocks on the face of the dyke the contract also includes work on increasing the size and capacity of the drainage pumping station built into the dyke which will allow a higher rate of discharge of the waters of the enclosed Ijsselmeer into the Wadden Sea which is the open sea area adjacent to the dyke. The two sluices that are incorporated into the dyke to allow water to flow in or out will also be replaced.

The concrete blocks being used to reinforce the dyke are being made to a new design that has been developed by Delta Marine Consultants (DMC) which is a subsidiary of BAM. Known as the Levvel Block after the consortium doing the placement work, these new blocks are the latest version of the X-Bloc armour unit that was also designed by DMC. This original X-bloc has been in use worldwide since 2004 to reinforce and protect breakwaters, dykes and other sea vulnerable structures.

The more advanced version that has been developed is called the X-BlocPlus and it is claimed to have the same capacity of the original blocks to absorb wave impact and protect structures but which uses less concrete. Instead of the blocks being dumped on the slope in an irregular pattern the new blocks will be placed with identical orientation and interlock.

This contract has been placed by the Rijkswaterstaat and is valued at €550 million and it includes the maintenance of the Afsluitdijk for 25 years after completion