Selective Withdrawal directs salt water back to the sea

High-quality panel and custom formwork systems For Selective Withdrawal in IJmuiden

Van Hattum and Blankevoort is building the Selective Withdrawal in IJmuiden on behalf of the Department of Public Works. Due to the use of the sea lock in IJmuiden, too much salt water flows into the North Sea Canal compared to the Noordersluis. The salt water has a detrimental effect on nature and agriculture, and the Selective Withdrawal construction should counteract the increase in salt water. A concrete dam will be built in the inner sluice channel that will form a physical separation. The dam will be approximately 90 meters wide and 13 meters high. Below this 13-meter-high wall is a "letterbox opening. Because salt water is heavier than fresh water, the salt water will flow back to the sea through this opening when the pumping station is activated. Van Hattum en Blankevoort entrusted Construx to design and supply all necessary panel and custom formwork for the realization of the above project.

The two concrete piers to be built were constructed using a combination of standard panel formwork and custom steel formwork. The specially designed climbing/lifting platforms were also designed and supplied by Construx. To avoid execution errors, Construx has chosen, in consultation with Van Hattum en Blankevoort, to work out the whole project completely in 3D. 

Panel and custom formwork

Both piers are 20 meters wide, 5 meters deep and 27.5 meters high. On the inside, the piers are hollow; they will be filled with sand at a later stage. Both the interior and exterior formwork of the piers are realized using panel formwork, which climbs 3.25 meters each pour. Special climbing decks were developed for the inside of the piers in order to be able to place the inside formwork safely and to realize the reinforcement of the piers. The tip of the piers has a radius that cannot be made with the standard adjustable circular rental formwork (Conflex). So for this, Construx designed a special steel formwork. 

At a height of 19.5 meters a complete floor is poured in the pillars. For this the Easydeck floor formwork is supplied by Construx. This floor formwork rests on the specially made climbing decks. The load of the concrete floor is completely transferred via the climbing decks to the specially designed climbing consoles. In the floor of the pillars, recesses are made so that the climbing decks and the Easydeck floor system can be lowered completely to the bottom of the pillar. An opening was left at the bottom of the wall of the pillars so that all formwork components can be easily removed.

Sunken

The piers will be constructed in their entirety on the quay, in the vicinity of the Sea Lock. After the piers are completed, they will be sunk into their final position by means of a lifting vessel, the Gulliver. The completely finished piles to be sunk will weigh 3,200 tons each. This action has been scheduled since the day Van Hattum en Blankevoort was awarded the contract for the work. Running out of schedule is therefore not an option. Partly to avoid surprises during the pouring, the whole thing has been worked out by Construx in a 3D drawing package. Both the special formwork and all system formwork parts are included. All parts to be poured, as well as the reinforcement, are thus checked for possible clashes. 

Partner

Construx acts on this work for Van Hattum en Blankevoort as a partner with a total solution, for example by also supplying all the necessary formwork parts for the three separating walls, the necessary fish passages et cetera. Partly because of the smooth and pleasant cooperation Construx would like to thank Van Hattum en Blankevoort for the trust placed in her.