The hub of the tunnel construction
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The starting shaft in Holma |
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The batching plant and the train that transport the pre-fabricated segments. |
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The segment depot |
South of the city centre, at Holma, is the heart of the tunnel construction process. This is where the tunnel boring machines starts. This is where the excavation material comes out and where the tunnel segments are manufactured.
At Holma, the bored tunnels changes to two 360 meters long concrete tunnels. The concrete tunnel is built into an open shaft and the tunnel portal at the transition between the concrete tunnel and the open ramp. The 390 metre long ramp is also built in an open shaft. The tracks then continue in a cutting seven metres below ground level southwards to Hyllie station.
Batching plant
The batchin plant in Holma supplies concrete for the entire tunnel construction – from the segment factory to the works at Triangeln station. The station has two mixers; one has a capacity of 1,5 and the other for 2 m3 concrete per batch. The process time per batch is a few minutes. This means that the plant has a capacity of about 600 m3 per shift.
Segment factory
The concrete segments for the bored tunnels are manufactured at a plant in Holma. Seven segments plus one lock-segment make one ring. Each segment weighs 5-6 tons and the lock-piece weighs 1 ton. The precision is very high: the tolerance between the segments is 0,1 mm. Each ring adds 1,8 meters to the length of the tunnel. This means that over 40,000 tunnel segments are needed for the tunnels.
The segments are stored at a depot outside the segment factory. A small train will transport the segments to the depot and the train will also transport the segments into the tunnel boring machines. There are always enough segments to support the continuous operation of the machines.