The first of the twin EPBMs boring the rail tunnels for Malmö’s Citytunnel project holed through last month to complete its drive at the central station – earlier than originally scheduled, and the second could breakthrough before the end of this month.
Slightly more than 4.6km was excavated by the 8.89m diameter Herrenknecht TBM named “Anna” over almost 500 days, said Bilfinger Berger, which is part of the Malmö Citytunnel Group (MCG) consortium building the project under a US$325M (2001 prices) design and build contract. Other members of the JV are Per Aarsleff and E Phil & Sons.
The TBM started excavating, in Holma, in late November 2006 and in late August last year it holed through at the intermediate, Triangeln station to complete the first, 2.7km long drive. At the station, the TBM was pulled through and overhauled before being relaunched in mid-November to bore the final, 1.9km long stretch to Malmö Central – Malmö C.
Anna’s sister machine, “Katrin”, kept pace in the range of 500m-600m behind and followed a similar sequence at Triangeln (T&TI, October 2007, p6). The contractor said that when Anna finished her drive the second machine had approximately 500m to go and was due to breakthrough in about a month, in late April.
Driving through limestone geology at depths of 20m-25m and with groundwater almost 20m above the tunnel invert, it was expected that the drives from Triangeln to Malmö C would present the more difficult tunnelling conditions, including more residential areas and a number of tighter turns. It was noted by the client at the time of the relaunch that following the experience of the first drive the public would be able to detect vibrations as structure-borne sound, for a few days, as the TBM grinded its way below their immediate area.
Previously, the client had said that the tunnel drives were expected to be completed by mid-year or the third quarter, and the anticipated hole through by Katrin would mean excavation was executed a few months faster than planned.
The running tunnels are being excavated some 10m-30m apart along the route, and the TBMs have been installing 350mm thick concrete segments (7+1) to form 1.8m long rings of 7.9m i.d.
The Client, Sweden’s National Rail Administration (Banverket) wants the entire project, which has a budget of US$1.3bn (2001 prices) to be completed by 2011. The project will connect Malmö’s central rail system with the Øresund bridge to Copenhagen, Denmark, and also tie into the Scania network.
Final breakthrough of the first TBM on the twin rail tube drives in Malmo Final breakthrough – 1 Final breakthrough of the first TBM on the twin rail tube drives in Malmo Final breakthrough – 2
