Widened A10 Zuid to rest on piled embankment

This month saw the first of around 3,500 piles inserted into the ground alongside the A10 Zuid. The length of each pile? 17.5 m. The total length of all the piles combined? Around 60 km, or twice around the Amsterdam orbital ring road. The piled embankment that the TriAX construction consortium (Besix, Dura Vermeer and Heijmans) is currently building on both sides of the A10 Zuid, next to the De Nieuwe Meer junction, is definitely not a standard structure. On top of the piles, there will be a veritable ‘mattress’ made from geotextiles (plastic membrane) with a metre thick layer of sand in-between. This enables the piled embankment to provide strong foundations, comparable to a concrete sheet. These foundations are needed to support the new lanes of the A10 Zuid, which we are building on top of them.

Simply adding sand and then building a new section of motorway on top of it is just impossible in this area. This is because the Amsterdam soils are soft, consisting of layers of clay and peat. Raising the height of it can cause subsidence: a 2 m layer of sand can sink by around 20 cm within just a few months. This is why TriAX has opted for the innovative piled embankment technique: the 17.5 metre-long piles run diagonally across the soft layers of soil to reach the strong second layer of sand. There is also another factor at play: space. There is very little of it, between the A10 Zuid and the existing buildings, such as Tripolis-Park and Infinity. There is not enough room for a sloping embankment, such as that built for the original A10.

Put briefly, the soil-nailing is done by digging up consecutive layers in strips lengthways from top to bottom. To enable the digging, we started by drilling in anchors, referred to as nails. Hence the term soil-nailing. As soon as the excess soil has been removed, the layer of earth behind it is reinforced with sprayed concrete. As soon as it hardens, an earth-retaining structure is created. You can then continue on the section underneath, and so on, until you reach ground level (or the bottom).

As soon as the piles for the piled embankment are in the ground, they are covered with concrete tiles measuring 1 x 1 m and around 40 cm thick. Don’t be mistaken – these pile caps actually weigh almost a tonne each. It is expected that all of the piles will be in the ground by the autumn of 2025. Geotextile will be rolled out on top of them, followed by a metre of sand. The membrane will then be folded back, creating a kind of package (like a mattress). A total of 450,000 sq. m. of geotextile membrane will be needed. By way of comparison: this is 54 times the size of the pitch at the Johan Cruijff ArenA. This will then be covered by a layer of granulate. When the road widening has been completed, there will be foundations in place that are guaranteed to remain stable.