The Rottemerentunnel is part of the A16 Rotterdam: an 11 km long highway between the A16 at the Terbregseplein and the A13 at Rotterdam The Hague Airport. It lies half-buried under the Lage Bergse Bos and the river Rotte. In 5 years, we have built the worlds 1st energy-neutral highway with a tunnel here.
A tunnel over 2 km long is not built just like that. We did it in 5 steps. Starting with step 1: placing the foundation and sheet piles.
Step 1: Sheet Piles and Foundation
Construction began in the autumn of 2020, with the installation of steel sheet piles to create the construction pit. We also drilled foundation piles, which ensure that the tunnel stays firmly in place. In total, we built 7 km of sheet piles and used 7,700 foundation piles.
Step 2: Excavating the Construction Pit
We removed the sand in the construction pit. While doing so, we added water to prevent the bottom of the construction pit from bursting due to groundwater pressure. A special team of divers in the construction pit ensured that the ground around the heads of the foundation piles was properly excavated.
Step 3: Reinforced Underwater Concrete
We poured the floor of reinforced underwater concrete. That sounds strange, concrete underwater. You might think that the concrete wont harden. But this is special concrete that actually needs water to harden. Here too, divers checked that the work was proceeding correctly. Once the concrete had hardened, the construction pit was watertight and we pumped the water away.
Step 4: Walls and Roof
Next, the concrete for the walls and roof was poured in sections of about 25 m. Between the 2 tunnel tubes, we made space for the technical installations and associated cables. There are quite a few: the Rottemerentunnel contains 54 different technical systems, such as lighting, barriers, fans, and speakers. In total, we use 100 different cables.
Step 5: Removing Sheet Piles and Green Landscaping
Finally, the sheet piles were removed, we poured soil on the tunnel tubes, and the tunnel roof slowly but surely became green again. As a cherry on top, the Lage Bergse Bos was renovated by the Recreational Board Rottemeren. The construction of the A16 Rotterdam accelerated this renovation of the forest. Good news, because now you can fully enjoy a varied area where there is so much to see, discover, and experience.
Sailing Over a Construction Site
During all 5 steps, we ensured that the river Rotte remained open. Both for shipping and for the drainage of nearby polders. We devised a construction approach where the Rotte could always remain half open. How did we manage that?
First, we worked on one side of the Rotte. We placed a sheet pile in the middle of the river lengthwise. This is how we built the 1st part of the tunnel. Then we moved everything to the other side and continued working there. Boats, canoes, and sloops could always pass by. Either way. While work was underway on the tunnel, you could still paddle on the water!