ABSTRACT
As part of the construction of Copenhagen Metro M4 line, an underground concourse hall is proposed at Ny Ellebjerg station (“CRSH6”), to enable passenger interchange between the new M4 metro line, commuter train lines (“S-tog” and “Ringbane”) and the regional train line (“Øresundståg”). As part of the overall M4 project, a future Over Site Development (“OSD”) is planned at this location, extending above and around the newly constructed metro infrastructure. Whilst the design of the OSD was in its very early stages, it was evaluated that some of the foundations for this structure would need to be constructed during the M4 line construction period (within CRSH6) in order to be feasible. The design of these foundations considers different development and loading scenarios from the OSD, and the impact on the M4 line tunnels – both during construction of CRSH6 and in the period during and following the OSD construction.To maximise the potential footprint of the future OSD, it was necessary to locate some of the foundations within 1 m of the M4 tunnels. Different foundation concepts were considered, and a detailed comparative risk evaluation was undertaken for the options considering the construction of the foundations and their impact on the M4 tunnels. This risk evaluation considered analyses of the likely tunnel movements and their associated impact on watertightness, structural integrity and railway operation. A solution comprising heavily loaded large diameter “conventional” bored piles within Bryozoan Limestone was chosen, with partially-constructed structural columns terminating at ground level to minimise the impact on operations during the OSD construction period.
