Foundations – an invisible stage

Every night when the curtain goes up, the stage pulses with the skill and creativity of the performers, set designers, directors and scriptwriters. Behind the scenes, though, there is another world, hidden from the audience. Modern technology ensures that everything goes according to plan on stage. But in addition to this, the theatre encompasses a third world – silent, invisible and still. It's task is to stay firm and stable under the stage and public facilities in the building's foundations deep in the ground.
Old theatre buildings are important landmarks of city centres and prestigious monuments that often enjoy special protection. Both in Amsterdam, Holland, and in Turku, Finland, the old wooden piles under the cities' theatre buildings are being replaced with Ruukki's piling solution, an option suitable for use in underpinning projects.

Carré Theatre of Amsterdam – a masterpiece of piling

After over 100 years of heavy use, during which approximately 27 million people visited the Carré Theatre, the Netherlands' most prominent theatre was in need of some serious interior and exterior maintenance. Victor de Waal, General Manager of Walinco and Funderingstechniek, two Dutch companies specialised in foundation construction, talks about the challenges and solutions concerning this prestigious project.

As one of Amsterdam's best-known landmark and most visited theatres, Carré's busy past had left its marks. Worn seats, draughty hallways and other general wear-and-tear had given management enough reason to consider renovation. But when surveys diagnosed the theatre's wooden foundation piles with a bacteriological infection, there was no time like the present.
Remarkably, foundation engineering specialist Victor de Waal initially declined.
"I didn't think we could do it. It was a large, difficult assignment that needed to be completed under an extremely tight timeline."
"If you're already planning a large renovation that requires you to reinforce your foundations, it's only logical to take the next step and fully underpin them. Alternatively, the theatre is faced with another period of closure and significant loss of revenue twenty years down the line. It's much more sensible to limit the amount of time you have to close your business than to be sparing with an investment you'll eventually have to make anyway," de Waal says.

There are two different water-related threats to Amsterdam, a city built on wooden piles. A possible hazard is a decrease in water levels, as dry piles are liable to rot within weeks. Fortunately, the old centre of Amsterdam has a relatively stable groundwater level.
The other is the bacteria. Opinions differ on the Best Before date of infected pinewood piles.
De Waal: "In my opinion, people are overreacting because the pace at which these bacteria affect the piles is rather slow."

Yet the project would not leave de Waal alone. Challenges regarding the foundations of old buildings simply fascinate him. The fact that it was a location as prominent as Carré made it even more interesting, especially because he lives across the river from the theatre and did not want to see a competitor do the work.
Funderingstechniek was asked to drive approximately two hundred steel piles – in less than four weeks, vibration free, and in a very small space. For example, space under the stage was so limited workers wouldn't be able to use pile elements much larger than one metre long. "While working in small spaces is one of our specialties, it does limit the size of machinery you can work with, decreasing the strength and consequently the speed of your work. That, combined with the high resistance of the soil on-site, made for a tough job that would normally take us between two and three months," says De Waal.

Coincidentally, Funderingstechniek has the same kind of soil conditions right outside its offices, giving it a perfect opportunity to run tests and compare techniques. De Waal's team adapted its machines and way of working accordingly until they had developed a suitable method.
"The technique needed for this assignment was already out there, we developed and refined it," explains De Waal.
"We combined all the factors: the weight of the piles, the degree of difficulty of the soil, the size of the machines and the speed at which we worked. This meant taking a big step further for us."
This is where Ruukki came in.
De Waal: "Ruukki supplied us with high grade steel piles that could be joined together by mechanical joints."
Specifically, Ruukki's driven RR piles and drilled RD piles are designed for use in underpinning projects.

Drilled piles are based on longitudinally welded steel piles and are extendable by means of mechanical joints, allowing fast connections. In underpinning projects and industrial construction advantages such as the small diameter and especially the splicing technique of the piles become increasingly obvious when the piling work is carried out in a narrow space. The installation equipment fits in the smallest of sites, and installation is not likely to cause any disturbance in the neighbourhood. In the case of shaft grounted piles used in Carré, grout is fed into the pile so that it seeps through holes in the pile into the cavity. Once dry, the grout transfers the load from the pile to the surrounding load bearing soil stratum, while also protecting the pile from corrosion.

Some parts of the building were so cramped the men had to pick up and transport every single pile separately. The pile elements provided by Ruukki had a total length of twenty metres, and the length of pile elements ranged from 2.4 to 4 metres. Ruukki delivered altogether 2.5 kilometres of piles to the site.

Ruukki has proven to Funderingstechniek to be a solid partner. "Reliability is very important," says de Waal. "When working under tight deadlines an unreliable supplier can cause serious delays."
"We have been working with Ruukki for six years now. They consistently deliver products punctually and they have an excellent price/quality ratio. Many other companies merely manufacture steel tubes and leave the rest to you. Ruukki is the only steel pipe pile manufacturer specialised in products for foundation engineering."

In a city as densely populated as Amsterdam, construction was known to irritate neighbours, especially as work was carried out in the early mornings, evenings and weekends. Thanks to successful information and Funderingstechniek's almost noise free equipment, complaints were kept to a minimum.

+From a circus to a hallmark theatre
+Repairing prestigios monuments
Story: Eva Rijser Photos: Jos de Vois

+Turku fights sinking by installing steel piles