350 piles for additional station passageway

As we walk underneath the roof of the new Brittenpassage, we catch a glimpse of an impressive machine as it rotates a 5 m long tubular pile into the ground. Once the pile has been inserted, a welder sets to work to weld the next one on top of it. ‘The piles form the foundations of the passageway floor and need to be 27 m deep in the ground’, explains Stephan Keizer, head foreman at the Nieuw Zuid Construction Consortium (BCNZ, Boskalis, Mobilis and Van Gelder). ‘But because of the limited height of the passageway, we’re drilling them in in sections. We then weld them to each other. It’s the same thing we did previously with the combi-walls on both sides of the passageway.’

Since the start of 2024, the south side of the Brittenpassage has been at the required depth: in the space of just a few months, BCNZ construction workers removed around 35,000 m³ of soil from underneath the A10, metro and railway tracks. ‘We’ve also finished installing the retaining walls (sheet piling to make digging possible Ed.) and removed the remnants of the so-called Amstelveenboog’, says Keizer pointing in the direction of the future entrance to the passageway in Arnold Schönberglaan. ‘What you can now see are the contours of the future passageway on the south side. Of course, we still need to start digging on the north side, where we’ll be looking at a mountain of sand for another few months.’

The number of piles on the south side has now reached around 153. Keizer: ‘As soon as a pile is completely in the ground, a reinforcement cage is added. We’re also doing this in short sections that we weld together. Once the reinforcement is in the tubular pile, a lid is placed on the pile. The concrete is not poured until later, because we have a lot of to-ing and fro-ing with heavy materials in the coming period. That will involve driving across some of the piles, so we’re covering them up first with driving plates that distribute the weight. They form a temporary construction road. At the end of March, we’ll gradually start pouring the concrete for the piles.’

In certain places in the Brittenpassage, more piles are being inserted into the ground – on the north-west side, for example, where we are building an underground bicycle storage facility. In the middle of the passageway, we are also building a row of footings across the entire length. These are very sturdy (underground) concrete structures. On top of them, we will later build the columns that will form the supports for the passageway. ‘They’ll need to support a lot of weight, so you can imagine that piles wouldn’t be up to the job here’, says Keizer. ‘These footings are actually like one big block of concrete 70 m in length and around 5 m wide, from north to south, but with interruptions every 15 m.’

The footings will go underneath the temporary supports in the passageway. Around these supports, slightly deeper digging is currently underway, to enable BCNZ to pour the concrete for the footings starting in mid-March. Keizer: ‘When the footings are finished, we can start building new columns for the passageway. After that, we won’t be able to simply remove the old temporary supports. We first need to ensure that the new columns ‘take over’ the roof sections from the old supports, as it were. To do that, we’ll raise the roof sections slightly using jacks and install definitive bearings between the columns and the roof sections. The old supports can’t be removed until that’s happened.’