Introduction

In 2011, Copenhagen embarked on a monumental project: Cityringen, a metro expansion that opened 17 stations in 2019. This project laid the groundwork for further expansion towards Sydhavn, adding five more stations and two shafts, including the Gåsebæk shaft. This extension is poised to become a vital traffic hub in Copenhagen’s public transportation network.

Challenges

Due to the complexity and uncertainty inherent in excavation activities, metro station and shaft excavations are often a high risky task for all neighboring surroundings. There are many challenges to take into consideration during the construction process.

As the excavated depth at Gåsebæk is 23 meters, controlling the groundwater during the construction work is very important. Another challenge at Gåsebæk is soil variation.

The soil at Gåsebæk varies a great deal as the excavation becomes deeper. In order to break through the different layers of soil and limestone, excavations involve various sources of vibrations. This includes pile driving, hammering with mechanical means, and others. The dynamic effects of such sources may create substantial vibration and volume loss problems for surrounding buildings and other infrastructure close by such as railways.

Groundwater management and soil variations are sufficiently challenging in regular excavations, but at Gåsebæk it is even more challenging. The construction site is situated close to a double-tracked railway that will be in operation during the excavation.

Changes in groundwater levels and vibrations from a construction site near-by may cause settlements in the railway. This poses a security risk.  As a result, the Main Contractor (TUNN3l JV) is subjected to strict safety requirements. This requires them to monitor the tracks closely with automated means so that neither groundwater, settlements nor vibrations caused by the excavation affects the railway.

Solution

To support the monitoring of the tracks, Railmonitor has delivered a wireless solution, TrackBed³⁶⁰, that allows for continuous condition monitoring. The solution consists of tilt sensors installed directly onto the track from where they monitor every track movement closely.

The sensors collect data every 30 minutes and the data is automatically processed in Railmonitor’s Digital Service Platform. In the platform, TUNN3L JV can get a quick overview of valuable insight. Insights that inform the relevant personal of any changes in the track geometry. This assures TUNN3L JV easy access to continuous and accurate information regarding the current condition of their railway doing the excavation. Providing instant alarms if or when any values exceed the allowable thresholds, for relevant stakeholders.

Railmonitor’s solution, TrackBed³⁶⁰, assures that the TUNN3L JV a constant insight into the current track condition. This enables them to meet the strict monitoring requirements associated with a railway in operation.

About TUNN3L JV

The French-German consortium, TUNN3L JV, 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 are also in charge of laying 4,5 km railway tracks.