The Nordhavnen metro line to be opened in 2019

In Copenhagen, Denmark a large industrial port is now being transformed into a super-modern waterfront city with attractive residential areas, an attractive “business quarter” and a distinct sustainability profile. The Nordhavnen (Northern Harbor) project took off in 2012, and the first residents and companies arrived in 2014. In the near future, the area will have room for some 40,000 residents.

To connect this new suburban area with the rest of the Danish capital, an extension of the new City Circle metro line is to be completed by 2019. Ultimately, an estimated 11,000 commuters are expected to travel between two new stations, Nordhavnen and Orientkaj (Orient quay), and the city center every working day.

The 3 kilometer extension line features a 2 kilometer long twin-tunnel with a diameter of 5.8 meters. The subterranean Nordhavnen station will have a direct pedestrian subway to the nearby suburban rail network. The Orientkaj station is situated on an above-ground section of the line, with the station itself built on pillars. Additional stations in the Nordhavn area are already being discussed.

Extensive vibration monitoring

The Copenhagen Metro system runs under the densely populated inner city with offices, residential buildings, historical churches with sensitive frescos, and at least one museum. During the early phases of the City Circle project, extensive vibration monitoring was carried out using INFRA equipment. 30 INFRA geophones and 12 noise meters were used simultaneously and moved in tune with the progress of the tunneling work.

The tunnel construction was managed from four separate worksites. One method involves the casting of secant piles in 15 to 28-meter-deep holes, forming the tunnel wall. The other involves the casting of so-called diaphragm walls. In both cases, the walls are covered with cement.

Two different methods were applied in the construction of the 17 metro stations en route. To establish sufficient background data for reference, vibrations were measured before the commencement of the actual construction work. In some locations, for example near culturally protected buildings, the triggering levels were set lower than the DIN 4150 standard, to be absolutely sure.

Active monitoring included direct SMS alarms indicating the measuring location, the vibration level and any divergences from the limit value. All data loggers also feature software for live reporting, sending data every five seconds to the centrally located computer. To facilitate reporting and discussions with everybody concerned, the results are presented in figures and easy-to-grasp graphics.