'We thrive when the environment is complex and difficult'

The Edge Technologies building in Eindhoven is founded on 170 soil displacement screw piles with a precast core reinforced with grout (a mixture of cement and water). "This combination offers a nice alternative; the execution is vibration-free and offers a better guarantee of the final quality of the shaft," says director Jan-Wim Verhoeff of contractor Franki Grondtechnieken.

In this pile type, a steel tube fitted with a loose drill point is screwed into the ground. During drilling, grout is pumped under the drill point. The grout provides lubrication and a grout shell around the pile. After drilling to depth, a precast pile is inserted into the steel pipe - a precast column made of high-quality prestressed concrete. The steel pipe is then filled with grout, after which the pipe is pulled. The precast pile encased in grout remains in the ground. Control of the execution is possible thanks to integrity measurements and control of the execution parameters. "Basically, with this precast core 100%, you have assurance that the pile shaft is good," says Verhoeff. "The process is fully monitored and the parameters that are important for quality are carefully recorded."

Good relationship

The execution of the work took about 6 weeks. Verhoeff: "We carried out the work with our own people and machinery; the precast piles were delivered to the site certified." In addition to great security, this pile type also has advantages when implementing a basement. By installing shorter elements, the pile heads are recessed below ground level so that they do not interfere during excavation. In addition to this precast variant, many projects are carried out with a poured variant. "That method is cheaper; knowledge of the subsurface is very important to make a good quality product. The ground conditions in Eindhoven were not a major challenge thanks to our extensive experience. Increasingly, vibration-free screwing is chosen because of the limited inconvenience to the surroundings. It is very important to search together with the client for the best method for each specific project. Together the technically best and most economical solution can be sought. Developing a good relationship with the client is very important for this."

Sustainability

Franki Grondtechnieken is part of the Franki Foundations Group, with offices in Belgium, France, the Netherlands and the United Kingdom. "People don't usually hire us just for execution," Verhoeff says. "We are capable of complete project supervision, from preliminary studies to engineering and execution, including in construction combinations. Of course, it often happens that the foundation plan is already ready. In the case of complicated situations, such as weak soil or complicated structures, we can always advise. We thrive when the environment is complex, including projects under BREEAM. We also invest in sustainability, with electric equipment and, when required, green steel or concrete."