Follo Line

The project consists of the longest twin rail tunnels in Scandinavia, connecting Oslo and Ski in Norway.

In the TBM (Tunnel Boring Machine) section of the Follobanen project, Ghella collaborated, in JV, to execute what became the longest railway tunnel in the Nordic region and Norway’s largest transportation project. 

The TBM tunnel consists of two separate tunnel bores, each 18.5 km long with an internal diameter of 8.75 meters. It connects Oslo and Ski and has become a key section in the development of the Intercity network. The tunnel is designed for trains to travel at 250 km/h between the two cities and was excavated using four large double-shield TBMs. These TBMs were named “Anna from Kloppa”, “Magda Flåtestad”, “Queen Eufemia”, and “Queen Ellisiv”, in honor of four of Norway’s most courageous and pioneering women.

From the construction site at Åsland, located halfway between Oslo and Ski, where facilities for producing concrete segments and mass transport systems were established, the four TBMs began their journey. In a massive cavern, the TBMs—each 150 meters long and weighing 2,400 tons—were assembled and began excavation, with two TBMs heading toward Oslo and two toward Ski.

The challenging task of tunneling also involved blasting caverns for the TBMs, cross tunnels (including a 2.7 km-long escape tunnel), and two 420-meter-long transport tunnels. The joint venture also built the railway technical installations for the project, except for the signaling systems. 

The tunnel boring was completed in February 2019 when the last two TBMs reached 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