Main role for collaborative work and preparation

Foundation and walls for RIF010

The run-up was long, but in April 2023, the first sheet pile of RIF010 finally went into the Steigersgracht. Foundation specialist Kandt bv from Nieuwerkerk aan den IJssel was brought on board by Mobilis to install the sheet piles for this exceptional project and to drill the foundation piles for the underwater concrete floor. Intensive contact, especially with Mobilis and earthwork company Verboon, was extremely important here.

For RIF010, Kandt did not simply install 340 meters of sheet piling from a drawing and drill 270 piles into the ground. "The involvement started at a fairly early stage," says project manager Bastiaan Verheul. "When developing the idea for a surf pool in downtown Rotterdam, there was already contact between co-initiator Mobilis and Arie Kandt, founder of the foundation company of the same name. That was initially purely to explore the possibilities and impossibilities of building a wall, a floor and a turbine in the Steigersgracht. We all know that a lot of water flowed through the Meuse before the plans became concrete, but in August 2022 Mobilis started engineering in earnest. That was an iterative process with a lot of back and forth, in which Kandt had a say in terms of the execution engineering options until there was a feasible design."

Torque pontoons

Implementation began with the construction of a ramp structure on the side of the Market Hall and a yoke to get the pontoon parts into the water damage-free. Verheul: "The 12.00 by 21.00 meter coupling pontoons we used were composed of 20 separate parts that were brought in by road. The yoke was needed to get those pontoon parts hinged from the quay into the 2.50 meters of water below. From the coupling pontoons, the sheet piling and piles were installed."

Schoor

The sheet piles were vibrated into the moat using a high-frequency vibratory block with variable moment. Verheul: "Most of the sheet pile walls were installed at grade so as not to hit the pile foundation under the existing quay wall, which was also at grade. The existing quay wall including the foundation remained completely intact. The tilt also ensures that in the moat the width of the wave pool remains as large as possible. We also had to take into account the trees surrounding the moat. Pruning was only allowed to be minimal, so that was fitting and measuring and putting planks in several here and there."

Save time

The next phase involved the pile foundation for the underwater concrete floor. "That's when things really started to get busy in the construction pit," Verheul continues. "As with quite a few projects, the execution period was under considerable pressure. To save time, a phased implementation of pile foundation construction and earthwork was agreed in close cooperation with Mobilis and Verboon. We had to drill a pile foundation vibration-free, Verboon had the task of making the cofferdam silt-free. With a second piling rig and giving each other as much space as possible, we were able to find a nice optimum and time without losing sight of safety."

Kandt drilled 270 Leka piles up to 23.00 m long into the bottom for RIF010, to lead and brace. All piles were drilled 2.00 to 4.00 m below water level at depth. Sheet piles in lengths of 8.50 m to 10.00 m were installed for the sheet piles. "To create a transition from the underwater concrete floor to the 'beach' on the Wezenbrug side, another sheet pile was installed so that a connecting floor could be constructed in a dry pit," Verheul adds. "This final piece brings an end to a great story in which the preparation and cooperation with the executing parties played a leading role."