Introduction

In June 2020, the tunnel boring machines Inge & Olivia departed from the construction site of the new metro station, Sluseholmen in Copenhagen. They are now headed towards Mozarts Plads (Mozarts Square). This will be their next stop on their journey towards Ny Ellebjerg – the final destination in the M4 line, going south.

The M4 metro line consists of 5 stations and the tunnel stretch between these stations is approx. 4,5 km. The line is an extension of the existing metro, the Cityring, which covers the city center of Copenhagen.

Challenge

Compared to other excavation techniques, tunnel boring machines (TBMs) offer higher levels of safety. However, they do not eliminate all risks.

Any construction that includes TBMs making their way underground beneath an entire city, carries some level of risk. Especially neighboring surroundings such as roads, railways, buildings etc. will become exposed to substantial vibration and volume loss.

As it is the case with most metro stations, the new station at Mozarts Plads will be an underground station. The construction of the station and metro tunnel will be carried out in a densely populated area. The area primarily consists of residential properties and offices. The TBMs will be drilling below several of these buildings. In one case, the TBM will be working just 7 meters below the basement of one of these buildings.

Naturally, it is the main priority for TUNN3L JV I/S to ensure the safety of residents in the area and the construction crew. To ensure that the stability of these buildings is not compromised during the excavation, the Main Contractor (TUNN3l JV I/S) has decided to install adequate monitoring systems.

Solution

TUNN3L JV I/S, the main contractor, chose Railmonitor’s TrackBed³⁶⁰ solution for this project, following two other successful metro line extension projects in Copenhagen: Metro Expansion, Metro Excavation and Groundwater Management – TUNN3L, Gåsebæk, Denmark & Maintaining Railway Stability Amidst M4 Metro Line Excavation – TUNN3L, Sluseholmen, Denmark.

With optical displacement tilt sensors from Railmonitor as well as prisms from another system installed on the building, vibration and settlement are automatically monitored. By implementing the latest technology, TUNN3L JV I/S is able to monitor the construction process itself and its impact on the surrounding environment, 24 hours a day.

The Railmonitor solution, TrackBed³⁶⁰, ensures that even the smallest signs of settlement/heave in the construction is detected. The sensor data is sent directly  to Railmonitor’s software platform, the Digital Service Platform. Any irregularities and exceeding of any limit values will be detected by the system and it will instantly notify TUNN3L JV I/S. This allows them to stop the construction work immediately until the cause of the alarm has been identified.

Below you can see how the sensors from Railmonitor have been installed.

About TUNN3L JV I/S

The French-German consortium, TUNN3L JV I/S, won the bidding on the construction of the M4 metro line. The consortium consists of HOCHTIEF Infrastructure GmbH and VINCI Construction Grands Projects. In addition to building five metro stations, TUNN3L JV I/S is also in charge of laying a total of 4,5 km tunnel and railway tracks.