Excavation of the twin bore tunnels for the Malmö Citytunnel rail project was completed last month when the second 8.89m diameter TBM holed through after the final, 1.9km long drive.
The Herrenknecht machine, named “Katrin”, was relaunched on the more difficult, final drive from Triangeln station to Malmö Central – or, Malmö C – in late December 2007. In total, the TBM excavated just over 4.6km in two drives.
Katrin was first launched at Holma in early 2007. The contractor, Malmö Citytunnel Group (MCG), completed the 2.7km long drive, to Triangeln, in September last year after which the TBM was pulled through the station and overhauled in preparation for relaunch to Malmö C.
Geology along the route comprised limestone and the drive at depths of 20m-25m was against groundwater almost 20m above the tunnel invert. The last drive was below more residential areas and MCG had to deal with a number of tighter turns in the alignment. Before relaunch, the client Banverket said that on the first run the public had detected vibrations as structure-borne sound as the TBM passed below.
Katrin was the second of two TBMs to drive the twin tubes, the first – “Anna” – which it followed mostly a month and some 500m-600m behind. Anna was launched in November 2006 and holed through at Malmö C in late March (T&TI, April, p7). The bores are lined with 7.9m i.d. segments (7+1) in 1.8m long rings.
MCG is building the Citytunnel project under a US$325M (2001 prices) design and build contract. Members of the JV include Bilfinger Berger, Per Aarsleff and E Phil & Sons. Banverket wants the full, US$1.3B (2001 prices), scheme finished by 2011 which now looks more promising. It had initially anticipated TBM excavation to be completed by mid-year or in the third quarter.
Final TBM breakthrough at Malmo C station