Follo Line
The Railway Tunnels of Records in Scandinavia
A new, 22-kilometre-long high-speed dual-track railway line linking Oslo and Ski, diminishing traffic in the periphery of the capital, and reducing the duration of commutes by 50%.
Norway
2015 | 2022
Awarded in 2015, the Follo Line project was carried out by Ghella between 2015 and 2022 in Oslo, Norway. The works involved the construction of two twin railway tunnels connecting the cities of Oslo and Ski. In the TBM-excavated section, Ghella operated in a joint venture to deliver the longest railway tunnel in the Nordic region, which forms part of the largest transport infrastructure project in the country.
The alignment consists of two parallel tunnels, each 18.5 km long, with an internal diameter of 8.75 metres, designed to allow train operations at speeds of up to 250 km/h and to serve as a strategic infrastructure for the development of the InterCity rail network. Excavation was carried out using four double-shield TBMs, assembled and launched from the Åsland site, located between Oslo and Ski.
The scope of works also included the construction of caverns, cross passages, an emergency tunnel and transport tunnels, as well as the railway technical systems of the project, with the exception of signalling systems. Mechanised excavation was completed in February 2019, with the arrival of the last TBMs in Ski.
A Few Numbers
The individual boring work of the 4 TBMs has lasted between 23 and 27 months, and in total the excavation lasted 100 months, involved over 750 workers and 100 engineers and technical staff, from 25 different countries. Åsland was the site of a base camp with lodgings for more than 500 workers, offices, a gym, and a cafeteria. It was also the site for the prefabrication of the concrete segments used to finish the tunnels, avoiding any traffic outside the site.
For this project we chose to excavate using a Double Shield TBM, with a diameter of 9.96 meters, instead of the drill & blast method, involving the controlled use of explosives, traditionally utilized in Norway. In fact, a TBM had not been used in Norway for over 25 years owing to the type of rock, considered too hard and too abrasive for their cutting heads.
“We didn’t just build, and continue to build, a huge and complex infrastructure project, which is now in its final phase with the installation of the railway system but we have also established a close cooperation with the Client and an amazing international organization. This is something for all of us to be very proud of.”
Luca Paioletti | Country Manager Norvegia