Constructing a new metro is an impressive achievement on its own, and the Copenhagen Metro Cityring is no exception. However, when the construction site is below a capital with an underground of immense geological complexity, extensive site-investigations are required, in order to secure the historical buildings founded on piles from damage. As it would turn out – the most extensive onshore site-investigations in the history of Denmark.
The extent of the planned site-investigations were so comprehensive, that one company alone could not perform the task and stay within the tight time schedule. In order to perform the site-investigations according to the timeline, Geo and Per Aarsleff A/S entered a Joint Venture in 2007. Over a three-year period Geo-Aarsleff JV conducted hundreds of deep geotechnical drillings in the streets of Copenhagen.
Thousands of samples, several kilometres of chalk core samples, and numerous binders with data were accumulated. Subsequently Geo-Aarsleff JV performed additional drillings and advanced investigations in areas, which required further knowledge of the soil and groundwater conditions.
The key to success is collaboration
Keeping 12 drilling rigs in check, and simultaneously ensuring the citizens from noise inconvenience, beyond an unavoidable level, not only required excellent planning, but also collaboration exceeding all usual standards of the industry. In addition, precisely the combination of an exemplary collaboration with the Metroselskabet and the authorities, the most skilled drillers in Denmark behind the controls of the drilling rigs, as well as a professionally prepared project organisation, were decisive factors for the success of the project.
In the more than 500 geotechnical drillings, carried out in the site-investigations for the Copenhagen Cityring, more than 14 kilometres of risers and well screens with diameters between 63 and 225 mm were installed.
Did you know that the chalk, in which the Copenhagen Metro Cityring lies, is between 61 and 65 million years old?
Did you know that during the last ice age a 500-meter thick layer of ice covered Copenhagen?
Geo handles geological material and samples ranging from 2 hours old to 200 million years old.
During the geotechnical site-investigations for the Copenhagen Metro Cityring, Geo carried out more than 500 drillings. Accumulated, more than 14 km were drilled in the underground; equivalent to the Round Tower stacked 402 times.
Geo’s participation in the construction of the Metro Cityring was further expanded, after the Copenhagen Metro Team was selected general contractor of the construction of the Cityring.
The Italian general contractor selected Geo as consultant and designer on all geotechnical and groundwater related tasks. A role, which Geo has had since 2011.
Geo’s geotechnical engineers have analysed all available data along the approximately 17 kilometres of tunnel tubes, with the purpose of optimising the design of the deep stations and shafts, as well as the lining of the tunnel tubes, and by doing so minimising the material consumption of concrete, steel etc. This is however only possible, if you involve all accessible geotechnical experience accumulated in the organisation – learn from the process, listen to the customer, and simultaneously accumulate new knowledge, supplemented with further testing of the soil properties, through advanced laboratory tests.
During the construction, Geo’s team of groundwater engineers established 3D computer models for all stations and shafts, with the purpose of predicting the impact of the dewatering on the surroundings, and through that determine the optimal design and layout for abstraction and reinfiltration of groundwater. All in order to prevent damages on the historical buildings in Copenhagen, as well as the many poorly founded buildings in the city.
Designing the Metro Cityring has brought new knowledge concerning the Copenhagen underground to the surface. A knowledge, which in many years to come will benefit Geo’s clients in projects of any size, when soil and groundwater need controlling, in order to avoid costly precautions.