The tunnel section of the Citytunnel project covers the stretch from Malmö C to just south of Annetorpsvägen in the Holma district. The total extent of the tunnel will be 6 kilometres. Four and a half kilometres will be bored using two shielded tunnel boring machines (TBM).
The bored tunnel comprises two parallel tunnel tubes with an internal diameter of 7.9 metres. A total of 13 cross tunnels are built between the two tunnel tubes. The distance between the cross tunnels is approximately 350 metres. |
The tunnel boring machines will bore two parallel, single-track tunnel tubes 20-25 metres below ground level, in other words boring work totalling 9 kilometres. The remainder of the tunnel will be constructed at the start and end of the bored section in open shafts.
Casting in an open shaft
That part of the shaft that faces Annetorpsvägen is the starting point for the boring machines that will bore in under Malmö towards Malmö C. Part of the tunnel stretching 360 metres will be cast on-site in the same part of the shaft. The earth that is excavated will be used to backfill around and above the concrete tunnel with the result that the land will be reinstated to its original condition. The tracks will then continue southwards approximately 7 metres below ground towards Hyllie station.
Ground water
The limestone rock through which the tunnel tubes are bored is highly water-bearing in many places. Since the tunnels are made watertight from the very beginning, lowering of the ground water is avoided from the outset in the construction stage and the operational stage.
The cutter head works under pressure to keep out the water. A shield seals the cutter head and backwards from the limestone rock.
Access shafts will be sunk in Stadiongatan and Kung Oscars väg to allow emergency services to access the tunnel in case of an emergency. The access shafts will be built in open excavations.
Structure-borne sounds
Vibrations are caused when trains are driven through the tunnel and are propagated via the tunnel tubes, the rock and the ground into adjacent buildings where they can the radiate out as audible structure-borne sound. This audible structure-borne sound is perceived by humans as a very low-frequency rumbling noise. The tracks in the tunnel will have anti-vibration mountings so that the noise levels will be reduced to those set by the Environmental Court.