Monitoring new stations

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Cautus Geo has extensive assignments on the Fornebubanen railway - "Absolutely crucial," says the developer.

11. 11th April 2025

Written by Rino Andersen

The stations on the Fornebubanen railway are being built deep underground. Cautus Geo is monitoring the structures and ground conditions - "Impossible to carry out without continuous monitoring," says geotechnical engineer Vegard Søderholm at Fornebubanen.

In December 2020, construction of the Fornebu Line began. It is being built in a tunnel from Majorstuen in Oslo to Fornebu in Bærum. The railway will be completed in 2029. It will then be able to transport 8,000 travellers every hour. The distance from end station to end station is just under eight kilometres. The journey time will be 12 minutes.

Cautus Geo specialises in geomonitoring. This involves automatic monitoring and alerting of natural hazards, the environment and climate, building and construction, transport and structures.

Six stations

The Fornebu Line will have six stations. They will be built at depths ranging from 12 to 43 metres. The construction pits will be even deeper. Several are located close to other critical infrastructure, buildings, busy roads and railway tracks. Three are being built at Fornebu. The rest are being built in Oslo.

- The use of real-time data ensures that we can quickly make decisions on the right basis if something arises," says Søderholm at Fornebubanen, which is the developer and has the same name as the railway line.

- Without instrumentation, uncertainty is higher. This would have resulted in more conservative solutions and more expensive construction pits. For us as a developer, it is also important that we limit the impact on the railway's neighbours. The larger construction pits we have would be unthinkable to implement today without continuous monitoring. It's important to collect data along the way. This ensures that the structures behave as expected," says Søderholm.

Contracts

Cautus Geo is one of Europe's leading technology companies in automatic monitoring of structures, land, water, climate and the environment. The company has developed a wide range of sensor technology and a proprietary web solution, Cautus Web, for automatic and continuous collection, processing, analysis and notification based on data from various sources.

There are many assignments on the Fornebu line. At Madserud, instrumentation for continuous and automatic monitoring was installed as early as 2022. The work there is now complete. All data is analysed continuously in the Cautus Web access solution. Threshold values have been set for alerts to the developer and the individual contractors.

- We have had an alarm. It came in the middle of last summer's holidays and was the result of strong solar heat. It gives us confidence in our sensitivity and shows that even small movements are picked up," says Joakim Haverstad, site manager at Implenia, which is busy building the new Skøyen station. There, the tracks for the Fornebu line will be more than 40 metres underground.

Comprehensive

- "We've had various assignments on the Fornebu railway for over three years. Some have been completed. Others are just getting started. It's about both structures and ground conditions," says operations manager Sigmund Brekke Langelid of Cautus Geo.

The instrumentation ensures automatic and continuous monitoring of, among other things, sheet pile deformations, deformations, loads on struts in construction pits, pore pressure and groundwater.

The biggest projects are now linked to the new stations at Skøyen, Lysaker and Majorstua.

- At Skøyen, two shafts with diameters of 30 metres and depths of 60 metres will be constructed close to buildings, roads, railways and the tramway. "The complexity is high. Real-time data and an early warning system provide security for the work we do," says Haverstad.

The Fornebubane contracts