The last of 24 tunnel breakthroughs on Copenhagen’s DKK6,000M ($759M) metro, achieved last month, marked the culmination of three years of difficult mixed ground tunnelling beneath the Danish capital and the celebration of a second world tunnelling record.
The six-strong, British-led contracting joint venture Comet, with its two identical DKK50M earth pressure balance tunnelling machines, has battled through ground ranging from loose, boulder-ridden sands and gravels to competent limestone with broad bands of hard flint.
The 16.6km of twin tunnel driving by the two 5.2m diameter NFM-supplied EPBMs, connects half a dozen cut-and-cover station boxes and nine large shafts dug in advance.
Led by UK contractor Carillion, with Britain’s geotechnical specialist Bachy Soletanche, Comet also includes Italy’s Astaldi, French firm SAE, Austria’s Strabag and local firm NCC Denmark. The final breakthrough came three weeks early due in part to unexpectedly fast driving.
Just days before, the tunnelling team had slashed its own world record, claimed last year for this type of EPBM, by completing 54.6m of tunnel in 24 hours – an increase of two, 1.4m rings.
First section of the metro. 13km overall, opens in autumn next year with the two-route network fully operational by spring 2003.
