Copenhagen Metro - pre-investigations for a new circle line

Abstract

Pre-investigations are carried out for a new Circle Line on the Copenhagen Metro in the period from late 2002 to spring 2004. The overall scope of the investigations is to elect the most suitable alignment, to determine the cost of establishing and to determine how existing forms of transport will be impacted. Main focus is on economy and traffic planning. Civil Works investigations play, however, a crucial part in assessing alignments, concepts and construction methods, to estimate the risks associated herewith and to estimate the construction costs. It is a prerequisite that the Circle Line is built as ''more of the same kind'', i.e. using project elements from previously constructed Metro stages. The Circle Line connects some of the most densely work and residential areas in Copenhagen and is connected to the majority of the largest railway stations in Copenhagen, that are not already connected to other Metro lines. The Circle Line is expected to replace a number of public buses in the streets, and will provide Copenhagen with an urban Mass Rapid Transportation System that will ensure Copenhagen citizens' mobility within the city throughout the 21st Century. The length of the Main Proposal for the alignment is approx. 14.4 km, all underground with 16 stations and 20 emergency shafts of which some also serve as ventilation shafts. Stations will be provided with island platforms and twin TBM bored tunnels will connect the stations. Six cross-over's are provided in underground caverns. In addition to the Main Proposal an alternative part-alignment in the City at Frederiksstaden, another alternative part-alignment at Oesterbro and three alternative part-alignments at Frederiksberg, in total forming 16 possible combinations are to be investigated. Preparation for two underground branch-offs from the Circle Line, a connecting tunnel to the existing Metro system and the location of the Control and Maintenance Centre above ground are considered. Geological conditions will pose extra challenges to the TBM tunnel boring and NATM cavern construction, compared to previous constructed Metro lines, and extra attention will be required to avoid settlements and ground water drawdown. Especially on the northern part of the alignment tunnels will have to be constructed under less optimal geological conditions. At some of the planned locations the limestone cover will be limited or non-existing. Most stations can be constructed as standard stations with only minor adjustments. Some stations require larger adjustments, and for one station a brand new station concept must be developed. Transfer tunnels between platforms on existing and new Metro stations are planned at two locations. These tunnels will have to be excavated close to and between the running Metro tunnels. In addition, a transfer tunnel at the existing railway station at Oesterport will have to be constructed. The tunnel at Oesterport will have to be constructed under difficult conditions below ground water level and live tracks. Construction of NATM caverns and transfer tunnels will be amongst the most challenging works on the Circle Line. (A). Reprinted with permission from Elsevier. For the covering abstract see ITRD E124500.