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In 2019, the construction of an additional extension of the metro in Copenhagen began. When the project is finalized, five additional stations to the metro will have been added.

On a cold Monday morning in February 2020, a ton-heavy tunnel boring machine was activated. The drill will dig underground in connection with the extension of the new metro line M4 to Sydhavnen. Once the excavations have been completed, these tunnels will connect the metro line M4 Sydhavnen with the M3 Cityringen.

In 2024, M4 will include metro stations at Havneholmen, Enghave Brygge, Sluseholmen, Mozarts Plads and Ny Ellebjerg in the southern part of Copenhagen.

The tunnel boring machine is now slowly, but steady, approaching its next stop: Sluseholmen.


At the construction site at Sluseholmen an underground railway is located just outside the worksite fence. It runs from the Copenhagen Central Station to the areas of Kastrup and Øresund.

The excavation and construction for the new metro tunnels of M4 is located below the railway. Railways placed on top of a construction site are always a challenge. It is especially challenging when the construction process involves an excavation as well.

The level of limestone in the soil at Sluseholmen is very high and thus has formed a dense layer of soil. In order to break through the tough layers of soil, the excavation at Sluseholmen involves various sources of vibrations. The dynamic effects of machines such as a tunnel boring machine may create substantial vibration and problems with volume loss on infrastructure close by – such as railways.


Safety is a top priority for TUNN3L JV/IS and their partners. Even the smallest movements can affect the overall safety of the tracks. It is therefore extremely important that the tracks are closely monitored. Any signs of settlements must be detected as early as possible. This puts high demands on the monitoring solution.

Railmonitor is currently supporting TUNN3L JV/IS with condition monitoring at one of their other construction projects. That project is also related to the new metro and is very similar to the conditions at Sluseholmen. Based on their experience with the Railmonitor solution, TUNN3L JV/IS decided to add it to their project at Sluseholmen.

The Railmonitor solution has been installed on tracks in both directions and we are covering a total of 120 meter (60 meters pr. track). Parts of the tracks are more exposed to the construction than others. This is referred to as the zone of influence. At the zone of influence, we have chosen to reduce the distance between the sensors. In a distance of 20 meters, a sensor is placed for every 3 meters. This enables TUNN3L JV/IS to intensify the monitoring efforts on the parts of the railway stretch that are within the zone of influence. The remaining part of the tracks is referred to as the zone out of influence. Here, the sensors have been placed for every 6 meters.

The sensor data is sent directly to the Railmonitor software from where TUNN3L JV/IS can access the collected data. The system will ensure to alert relevant project managers the moment the sensors detect any deviations from set values. This empowers TUNN3L JV/IS to act before any potential failures have time to evolve into something critical. Thereby, ensuring the overall safety of the railway as well as the construction site always.


The French-German consortium, TUNN3L JV/IS, won the bidding on the construction. The consortium consists of HOCHTIEF Infrastructure GmbH and VINCI Construction Grands Projects. In addition to building the five stations, TUNN3L JV/IS are also in charge of creating 4,5 km of twin tunnels.

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