Trelleborg devises ingenious solution for walls Selective Withdrawal Sea Lock IJmuiden

Selective Withdrawal Sea Lock IJmuiden is a special project where Trelleborg Marine & Infrastructure's Design Engineers were also called upon for their solution-oriented abilities. It was a leap of faith involving the necessary calculations. Olivier Schuringa, Design Engineer, and Bob Rijnders, responsible as Global Sales Manager Water Infrastructure at Trelleborg, explain why their solution is crucial for the operation of the salt dam.

The more complex, the better. They love that at Trelleborg, "Because," says Olivier, "our strength is coming up with solutions to problems and issues in the field of polymers." A good example is the question from Van Hattum and Blankevoort, main contractor Zoutdam IJmuiden: Can Trelleborg develop a solution that absorbs the required forces and rotations, so that the walls of the salt dam do not move in their rebates during their lifetime but also that during installation this solution can take into account the placement and construction tolerances of the screens?

Finding boundaries

To meet these two requirements, we eventually arrived at a combination of a lifting cushion and imposition, Olivier explains. "The imposition captures the forces during any rotations caused by currents in the water, for example. The lifting cushion bridges the gaps to connect the overlay." During the design process, we had to continually push the boundaries of both the manufacturable and the workable. For example, on the one hand, the lifting cushion-layup combination must be as thin as possible so that there is maximum space during installation to lower the wall into the rebate. At the same time, in order to absorb all the forces after installation of the walls, the lifting cushion-laying combination must be maximally inflatable, so that the overlay block connects everywhere in case all the tolerances build up on one side. Basically two contradictions that we had to find a solution for. The combination we finally came up with was therefore extensively tested. Partly because we wanted to know exactly which filler would be most suitable for the lifting pad. After all, it must be controllable to inflate, even under water, and it must harden relatively quickly but not too quickly either. In addition, it is essential that the solution be right the first time. The moment the walls are installed, there is no turning back. It must also last throughout the life of the salt dam."

Cooperation and trust

Looking back on the entire design process, Olivier and Bob are proud of the fact that they were able to develop a solution to a particularly complex question. "That it succeeded is due to the good cooperation and trust that Van Hattum en Blankevoort gave us. In fact, the solution is so unique that we called it the Van Hattum and Blankevoort imposition."