Machine name: NLUTSRSP03

At 10 am in the morning on Thursday, 24 September, Combinatie Strukton/Van Oord (CSO) allowed water to flow beneath Amsterdam Central Station for the first time in 180 years. This was a milestone for the North/South Line. A ‘canal’ has been created directly under the centre of the monumental station building, through which the metro will soon travel. It is essentially a trench. The first waters were pumped from the IJ into the trench today. The process will be gradual and should be completed by 10 pm tonight.

First dry, then wet
The trench beneath Central Station was dug out as a dry construction pit to its current depth of six metres below Amsterdam Ordnance Datum (NAP). The last part of the excavation, to a depth of 19 metres below NAP, will take place under water. The trench is now being flooded to the level of the water in the construction pit between the trench and the IJ, which serves as a sluice gate. The water there is three metres below NAP.

Exceptional support structure
In order to make it possible for the North/South Line to pass beneath the station building, Combinatie Strukton/Van Oord replaced the original flooring and foundations with a special support structure. This structure looks somewhat like a massive underground table, strong enough to carry the central section of the station. The trench is being excavated underneath this table.

Connection
The water will remain in the trench until it has been completely excavated. A direct connection will then be made with the IJ so that the 130-metre-long tunnel section (the actual metro tube) can be floated from the IJ into the trench. The tunnel section has been ready for some time. Once the tunnel section is in place, the trench around the tunnel section will again be filled with sand. And, once the De Ruyterkade bus platform has been constructed and the immersed tunnels installed in the IJ, the connection with Amsterdam North will be a reality.

Technical challenge
Construction of the trench beneath the station has been one of the biggest technical challenges of the project to date. The station, which dates from 1889, is constructed on approximately 10,000 wooden poles. In ordered to prop up the building, the old poles in the area of the trench were replaced by a new wall under the Central Station building and 90 steel piles under the emplacement. Using new microtunneling technology, the piles were nonetheless drilled to a depth of around 16 metres in the limited space available under the station. These activities were carried out beneath the train tracks without causing any damage to the monumental building or obstructing the trains.

General
The underground composition of the station island is complex due to its layered makeup and limited load-bearing capacity. The upper layer consists of sand raised by hydraulic fill from the IJ.
The mixture of soil and water brought to the surface during the last part of the excavation will be fed off in pipes to boats in the IJ. The boats will then transport the mixture to a dumpsite for further processing.
One of the phases presenting the highest risk to the station building has since been completed. This involved the transporting by Civiel.

Press release 

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