Story so far
"I've learnt a lot in a short period of time, and not just about foundation engineering. I'm glad I'm here. And I'm also proud that I was allowed to participate in such a large project." Michel Willemen, trainee at HSL Combinatie Zuid-Holland-Midden - the company that is building part of the Dutch high speed railway line - is clearly having a good time. After his final work placement period from the Civil Engineering department of the MTS (intermediate technical school) in Leiden, Willemen is now working in the planning department of the HSL construction consortium that consists of the contractors Heijmans Funderingstechniek, HBG Civiel Grondtechniek and BAM NBM Funderingstechniek. When he returns from his holiday, he will take the civil engineering course at the HTS (institute of technology) but he has not yet decided which direction to follow.
The site hut is located on the outskirts of Rotterdam airport and the part of the project that Willemen is working on is the future railway line that will run from Schiebroek to the connection with the tunnel that has been bored under what is referred to as the green heart of the Netherlands (HSL 2). A 22-km section, consisting of a tunnel (from Schiebroek to the Doenkade), a semi-sunken open-topped tunnel, a deeper sunken open tunnel, a viaduct (which takes the high speed line over the A12 motorway) and a 4.5 km connection with the bored tunnel which is constructed as a settlement-free slab. Willemen's activities along the whole of this HSL Cluster 3 section are concerned with foundations.
Michel Willemen is responsible for calculating the amount of grout that is needed for the vibro combination piles that are being employed. These piles form part of the work placement report he has written for the intermediate technical school. He enthusiastically talks about this subject: the steel tube, that is driven into the ground, the pile ("sixteen to eighteen metres long, 450mm square, they're big things") that is placed in it, the grout and how it flows and grips the clay as the tube is removed. "They're just like little claws. Open tunnel sections such as those that are used here can be forced upwards by the groundwater, so the piles must also cope with the force created as the tunnel tries to float. It is very fascinating. And I'm also proud, that I am allowed to participate in such a large project. I sometimes wonder: if we didn't exist, I mean the foundation people..."