Tunnel excavation is complete for Norway’s Follo Line Project

The two tunnel boring machines (TBMs) of the four that the ACCIONA-Ghella Joint Venture (AGJV) has used on this project, reached the Norwegian town of Ski on Tuesday 26 February 2019, completing the TBM drilling work. The other two TBMs completed their work in September 2018.

The Follo Line Project will connect Oslo and Ski and allow trains to travel up to 250km/h.

The four machines, each one 150m-long and weighing 2,400 tonnes, started out from the same point in the Norwegian district of Asland, from where two of them drilled south towards Ski, and the other two drilled north towards Oslo.

One of the greatest challenges for the project has been the extremely hard rock, which has made drilling work difficult, combined with ground weakness in other zones. The cutting discs on the head of each TBM front-end penetrate the rock and the excavated material is then transported along the tunnel on an underground conveyor belt until it reaches the outside. As the cutting head drills through the rock, the rear section of the TBM installs the tunnel lining rings.

AGJV Project Manager, Fernando Vara, said: “AGJV has worked extremely hard of which we are proud, delivering quality, safety, innovation and experience. We have excavated more than 18km of tunnel and have delivered them on time, fulfilling our commitment. We have faced important challenges related to the ground conditions drilling towards Ski and we feel proud to be part of such a demanding TBM project. We are now entering a new phase, confident that we will once again do an excellent job.”

Once full excavation work of the tunnels has been completed, AGJV will carry out the railway installation works, except for the signalling systems. The planning phase for these activities has already begun and the concreting works, the preparation of the tunnel walls and the catenary systems, and the walkways and the technical rooms will all be carried out in the coming months. The telecommunications systems, installation of the tracks and the power supply and ventilation systems also form part of this project.

The Follo Line Project is the largest transport project carried out in Norway to date, and is part of the wider inter-city development plan for south-east Oslo which seeks to improve and develop the country’s transport infrastructures and is due to be completed by December 2021.