The two roof sections that we will be pushing into position on 21 August are ready and waiting. They were built in situ, because they are too long (70 m) to be transported. The construction site is located between the metro tracks and is very tight for space. That will be our first immediate challenge. After all, how do you shift two concrete structures each weighing more than a million kilogrammes if the room for manoeuvre is no more than 70 cm?
Creeping roof sections
‘We use hydraulic jacks to push these kinds of heavy structures into their final position’, explains project manager Koen Wichertjes. ‘Because there’s so little space next to the deck, we start by using smaller jacks than usual. These so-called mini-grippers push the roof section 5 cm forward before withdrawing for the next 5 cm step. In the first few hours, the two roof sections slowly creep towards their destination, centimetre by centimetre, until there’s enough room to use larger jacks.’ The two sections of the roof need to be moved 15 m to reach their ultimate position, underneath railway track 4 and metro track 1. ‘The heavier jacks really enable us to make progress. The final 13 m will probably take as long as the first 2 m.’
Trains and metros will run over the roof section. This part is where the trains running on track 4 will be. It is being made water-tight in order to ensure that the passenger tunnel below stays dry.
In November 2019, Wichertjes and his team also inserted a section of the roof into position, diagonally across the A10. ‘It was a totally different situation. We had a spacious construction site on the south side of the A10. Even before the weekend it was put into position, we pushed the huge deck around 30 m forward, to reach the A10 embankment. For the remaining 50 m, that first roof section achieved a speed of 10 metres per hour. Now, it’s a case of having to put the brakes on before you’ve even got going.’
The roof of the new Brittenpassage, the additional passenger tunnel at Amsterdam Zuid station, will comprise seven sections in total. Trains and metros will run over it. In theory, seven roof sections should mean the same tricky manoeuvre seven times: inserting foundation piles into the body of the dyke where the tracks are, building and attaching abutments, building roof sections, removing the track and then pushing the roof sections into their final position. That’s the theory. But, in practice, each of the seven roof sections requires its own bespoke approach, says Wichertjes. This is not only because there is much more limited space this time. ‘We’re now pushing two connected roof sections forward, while the metro and railway are still running. That’s another reason why this is precision work.’
Part of the roof section is not only where the track will be, but also a section of new platform. In this case, the platform along which railway track 4 runs. The white line shows the edge of it.
Want to watch live?
If you would like to watch the work during the weekend of 21/22 August live as it happens, we are organising a live event on the platform next to the work for anyone interested. You will be able to register for this soon. Of course, you can also watch it on the webcam.