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Catching up in

Publishing Date 18 Oct 2013 5:54pm GMT Author

Summary Rodney Craig provides an update on the Copenhagen New Circle Line after two years of construction The owner for the is Metroselskabet, company that is owned by the state (50%), Copenhagen Municipality (42%) and Fredriksberg Municipality (8%). The day-to-day running of the metro is let to Ansaldo of Italy.

Metroselskabet’s consultants for the civil and architectural works are a joint venture between COWI (), Arup (UK) and Systra (France). The systems consultants are a joint venture between Rambøll (Denmark) and Atkins (UK). The civil works contract was awarded in January 2011 to an Italian joint venture between Salini, Techimont and Seli (CMT, the Cityringen Metro Team) and the systems contract, with 28 new trains, was awarded concurrently to Ansaldo, which will also run the Cityringen (Circle Line) for five years.

The Cityringen

The Cityringen, which is scheduled to open in 2018, will have a total length of 15.5km and will have 17 underground cut-and-cover stations, four shafts and two crossovers. In addition there is a 1.5km-long spur to the surface to the depot and control centre at Vasbygade.

A spur to the north harbour designed by Rambøll, Atkins and architect COBE, which has two 2km-long tunnel boring machine (TBM) drives, a cut-and-cover station and a length of elevated alignment, has recently gone out to tender. Opening is planned in 2019. A spur to the south harbour is also under consideration.

There will be interchange with the existing fully automated driver-less trains on lines M1 and , which were inaugurated in 2002 and extended to the west in 2004 and to Copenhagen airport in 2007, at and at Fredriksberg; the new line will also interchange with the suburban and main lines at Copenhagen Central, Nørrebro and Østerport.

The Cityringen consists of two lines: M3, the full circle with trains at 200-second intervals, and M4 on the eastern section between Nørrebro and Copenhagen Central, also at 200-second intervals, giving 100-second intervals on this section of the alignment. Trains will take 24 minutes for the full circle. It is estimated that 72 million passengers a year will use the Cityringen, compared with 50 million a year between the existing metros M1 and M2.

Station specifics

All the stations are underground cut-and-cover structures, some of top-down construction and some bottom-up. The stations will have a main entrance at one end with two lifts from ground level to platform level, with a secondary entrance at the other end with a fixed emergency staircase exit, a draught-relief shaft and ventilation fans. Lines M1 and M2 have only one lift at the main entrance, which has been considered to be inadequate.

Generally, each station is 64.4m long by 20.4m or 22.4m wide with a 44m-long platform to accommodate three- car trains or four-car trains if additional capacity is later required. High-flow stations will have a 9m-wide island platform and other stations a 7m-wide island platform. The stations generally have an excavation depth of up to 24m but some are deeper at up to 35m and some shallower.

All the stations are currently under construction. The ground-support walls are constructed either with cased secant piling, the first use of this type in Copenhagen (at 10 stations) or diaphragm walls (seven stations). These cut-off walls have a minimum depth of 5m below the baseslab level, and are generally 28m deep. The secant piling or diaphragm walls are being installed by Italian sub-contractor Trevi, which is undertaking all the main foundation works.

All stations have groundwater recharge as the existing water table has to be maintained, since lowering of the water table is not allowed. Many of the buildings in Copenhagen are founded on timber piles and damage would be caused if the water table was lowered. Water recharge is being used with between 90% and 100% of the Seite 2 von 3

water extracted within the stations being treated and topped up before being used for recharge. The ground- water control is being managed by sub-contractor Hoelscher of Germany.

“Some of the station sites have major site constriction with low headroom or are close to buildings, churches and balconies, which have required special techniques,” Guy Taylor, project director of Metroselskabet, comments. “Low-headroom rigs have been used in some of these locations.”

Monitoring of the diaphragm walls and secant piling with inclinometers, stress measurements in the struts, settlement readings outside the stations and above the tunnels, water levels and noise and vibration levels are being carried out on a real-time basis with all the data going to the main offices for analysis.

Efforts to achieve completion of ground engineering works ahead of schedule have proved challenging and are now acknowledged as taking longer than expected. The project schedule and sequencing of the works has been adjusted to take account of this. The project is still on track to be completed by the end of 2018.

At the Sønder Boulevard site there is benzene-contaminated soil from an old gas works, which requires two desanding plants for the diaphragm walls, one for the contaminated ground and one for the natural ground. The box is 90m long by 15m wide. The diaphragm walls here are 1.2m thick and 2.8m wide and installed to 41m depth. At this location the two tunnels are one above the other rather than the general case of side by side.

Noisy times ahead

The main concern at the moment is noise and the restriction on the working hours. Between 07.00 and 18.00 there is currently a noise-restriction level of 70dB(A) and between 18.00 and 06.00 the level is 40Db(A). In June 2013 the city council approved an application to extend the working hours to 22:00. However, affected residents complained and since July the contractors have been forced to stop work at 18.00 at several of the stations. Residents near some of the sites have been offered compensation and money to install sound insulation in their homes.

However, residents near Nørrebroparken where 24-hour tunnelling works are planned have also lodged a complaint. Metroselskabet stated that if 24-hour working is not allowed, the Cityringen will be six years late and not opened until 2024 with an additional cost of DK9 billion (US$1.4 billion).

It will take the environmental appeals court some six months to process the complaint. Recently, according to the local press, the city council has opened up the possibility of letting the construction go ahead on a 24-hour basis. The city council has just started 10 days of public hearings, before a decision is taken. At all stations wooden noise barriers have been installed to reduce noise levels. There are also movable sound barriers being used to reduce noise levels.

Bored tunnels

The contractor has chosen to have four earth-pressure balanced TBMs, designed by Seli of Italy, in a partnership with Japanese player Kawasaki, with parts manufactured in Japan and in Italy. The first TBM was assembled in Italy before being shipped to Copenhagen. The first TBM arrived in December 2012 but has only recently started the drive. The second TBM is on site and assembly started in the pit in early September. The drive is from the Nørrebroparken site. The third and fourth TBMs are expected on site by the end of the year and starting in January and March 2014.

Tunnel details

The internal diameter of the ring is 4.9m. The rings are 300mm thick, 25mm thicker than for M1 and M2, and have a width of 1.4m and with rebar reinforcement. A carousel system with steam curing has been used for the casting of the segments. The rings have EPDM gaskets in the joints.

“The first sets of moulds were found to have been distorted after 450 rings had been manufactured and a new set of moulds was then ordered from Herrenknecht. This problem has now been solved,” Søren Degn Eskesen of COWI, and the recently appointed president of the International Tunnelling and Underground Space Association, explains.

The segments are manufactured at Satnitz, in Germany, by sub-contractor Mobil Baustoffe and are shipped in batches to Copenhagen every three weeks before being taken to the tunnel sites by lorry.

It is hoped, subject to approvals, that the TBMs will be working six days a week, 24 hours a day with maintenance shifts taking place on the seventh day. The design of the tunnels does not include any cross- passages between stations.

Compensation grouting is being considered to minimise settlement during construction above the tunnels.

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What lies beneath

The geology under Copenhagen consists of Danian limestone overlain by glacial deposits and fill. The glacial deposits have two layers of till with the upper layer separated from the lower level by meltwater deposits. The tills are heavily over-consolidated sandy clays with boulders and sand lenses.

The Copenhagen limestone of the Danian period has three layers – upper, middle and lower; the upper layer has a band of flints 200-400mm thick and sometimes larger. Along the tunnel route the south alignment will be in the limestone and the north alignment in the glacial deposits. A detailed and staged site investigation was carried out along the route including 374 boreholes, 246 geophysical logs and 600 pumping tests and many laboratory tests.

The ground water is 1m to 2m below the ground surface. A two-year groundwater programme was established before the letting of the contract, which will form the basis for targets for groundwater levels during the construction.

TBM specifications External diameter 5.78m Excavated diameter 5.88m Length of TBM 10.7m Total weight of TBM 500t Length of backup Approx. 73.5m Weight of backup Approx. 220t Number of disc cutters 38 Size of disc cutters 17in (431.80mm) Variable speed 0-5 rpm Max cutter torque 4.79kNm to 2.3rpm Installed power 1,200kW Number of rams 16 Stroke of rams 2.2m Max working thrust 36,490kN at 300bar External diameter of screw 775mm Length of screw 13.75m Screw conveyor installed power 250kW Screw conveyor capacity 255m³/hr Screw conveyor rotational speed 0-24rpm Lifting system of erector Rotary ring type with longitudinal travel along tunnel axis

The author would like to thank Guy Taylor, civils project director of Metroselskabet, and Søren Degn Eskesen, tunnel manager of the COWI-Arup-SystraJV, for their assistance, for the site visit and for the illustrations

© Aspermont UK (Mining Communications Ltd) Albert House, 1 Singer Street, London, EC2A 4BQ