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Photographer's Note

In the background, you see Amsterdam Central Station but today, the picture (and WS as a "bonus") is about the new metro-line:

The Municipality of Amsterdam is developing the North/South Line, a new metro line that will connect Amsterdam North with the Amsterdam South/World Trade Centre (WTC) Station in 2011. Construction began on the 17 January 2003. The project will cost approximately US$1 billion. The metro line will run from Amsterdam Noord to Central Station, the inner city and De Pijp to Zuideramstel. It will measure nine and a half kilometres long.
In the north the line will run partly above the ground before descending below ground level just in front of the river IJ. Along the length of the metro line, the two tunnel tubes run parallel horizontally. The route is too narrow for parallel tunnels at one point and thus the two tubes will run vertically parallel, one above the other. The line alignment will reach a depth of 20 to 34m below the narrow streets, historical houses and bridges, and sewer.
A downward construction method with diaphragm walls has been employed in the construction of the underground stations. During excavation, cast in-situ concrete roof/floor slabs are used as the lateral support for the diaphragm walls. Starting from the top, excavation and concrete slab casting are carried out alternately.
The construction of the underground metro line is being completed through the adoption of an open excavation method for the shallow depth sections of the metro line, and a downward construction method with diaphragm walls or drilling method utilizing tunnel boring machine for the deeper sections of the metro line.
For the construction of the underwater sections of the metro line, pre-cast concrete boxes are being sunk into the river, with or without prior riverbed excavation.
The metro line is being bored from the Damrak. Following the street pattern under the inner city of Amsterdam, the Tunnel Boring Machine (TBM) prevents any houses from being razed. The boring taking place 20m to 30m below the ground will be unnoticeable to passers-by.
The TBM will be put together in the construction site located in the water of the Damrak. The TBM has a diameter of six and half metres as well as a length of 40m. The head of the TBM consists of a shield and an eight metre long hollow steel cylinder. This is where the tunnel-builders work. The shield protects the tunnel builders from the ground and the groundwater.
The TBM covers approximately eight metres in one day. Metal rails are also being laid in each new partition. Over these will ride the work train, transporting the material and workers.
Because there are two metro tunnels being constructed, two TBMs are needed. The two TBMs are not operating at the same time. When the first TBM has been operating for approximately three months, the second TBM will be brought into the ground. The boring, including all of the preparation and finishing, will take about 50 months.

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Additional Photos by Hans Stellingwerf (Hanssie) Gold Star Critiquer/Gold Note Writer [C: 2131 W: 2 N: 2030] (11018)
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