Extended A16 | 10,000 piles under tunnel

'Great works you fund together'

With trusted parties it is good building. Franki Grondtechnieken and Voorbij Funderingstechniek have been active for some time on the Theemweg route in the Rotterdam port area. Currently the two companies are once again working together on a major infrastructure project, this time on the north side of Rotterdam. Here, foundation combination FCVF is providing the foundations for the freeway that will connect the A16 and A13 motorways for combination De Groene Boog.

Jan-Wim Verhoeff, general manager of Franki Grondtechnieken: "The cooperation on the Theemstracé is going very well. Since our parent companies Besix and TBI/Mobilis are also part of the construction consortium on the A16 Rotterdam, a continuation of the cooperation was obvious. These are both projects which, because of their enormous size, place such heavy demands on people and equipment that you can't escape working together. We complement each other well: Franki specializes in vibration-free drilling, Voorbij is strong in sheet piling." Total number of piles: 12,500; total sheet pile weight: 20,000 tons.

16 statements

The new stretch of the A16 has 25 temporary and 35 permanent structures, including the more than 2-kilometer-long sunken tunnel trench. Verhoeff: "At its peak, 16 scaffolds are active in the tunnel. Franki and Voorbij supply a number of them and if necessary we look in the market for replenishment. That way we don't have to disappoint customers on other projects. We are currently working on the abutments of the fly-over at Terbregseplein and preparing the tunnel trench, where sheet pile walls are being installed."

Sound

To minimize the inconvenience to people and nature, in principle, vibration-free, low-noise techniques such as soil displacement screw piles are used, whether or not in combination with a precast element. Sheet piling is pressed down as much as possible. This will relieve the environment, but also nature, as much as possible.

More than 10,000 posts

The largest volume will soon be under the tunnel trough. Verhoeff: "More than 10,000 piles of 25 to 30 meters long are needed for the more than 2 kilometers of semi-sunken tunnel trench. We use combination piles for this, in which we first drill a tube of (for example) 25 meters into which a prefab element of 20 meters length is placed. Then, after pulling the tube, you can easily excavate 5 meters to make a construction pit. The first open ditches of the tunnel will have the same foundation. The piles also have a pulling function. The soil here is so soggy, it's like walking on water. This makes the closed tunnel box want to float."

HSL

Another challenge lies a little further down the road when the A16 Rotterdam has to cross the HSL. This railroad line is founded on a layer of sand at a depth of 25 meters. Verhoeff: "We are not allowed to use that layer for the overpass because it could affect the stability of the railroad tunnel. That's why we are going with 60-meter piles through the first layer to the next layer of sand. Safety first."
The foundation combination will be busy for De Groene Boog until the middle of next year. Verhoeff: "We have a very tight schedule. Through good cooperation with De Groene Boog we do everything we can to respect the project schedule and make a good job of it together, therein lies our strength!"