Extending Cityringen – the challenges involved

In 2011 a contract was signed for the construction of Copenhagen's new metro line, Cityringen, which will connect 17 new underground stations in and around the centre of Copenhagen. To assist with the development of the city it was decided in 2012 and 2014 to add branches to Cityringen connecting the city centre with north and south harbour areas, respectively. This required the introduction of bifurcations to connect the branches to Cityringen tunnels. The bifurcations were made with the substantial modification of a shaft at Øster Søgade and the introduction of a new shaft, Havneholmen. This paper outlines both engineering and logistical challenges introduced by these changes, from the construction of a 35 m deep shaft around existing stacked tunnels adjacent to an operational railway line to how the closing tunnels for the construction of the shaft impacted the tunnel installations and the overall time schedule, plus numerous other issues.