The Follo Line project will connect the city of Oslo with the town of Ski via twin 19.5 km tunnels, the longest in Scandinavia.
ACCIONA and Ghella have completed the excavation works of the twin 19.5 km and 8.8 metre diameter railway tunnels for the Follo Line project, which will create an infrastructure that connects Oslo and Ski and allow trains to travel up to 250 km/h, improving communications between the residents of these two centres.
The two tunnel boring machines (TBM) of the four that the ACCIONA-Ghella Joint Venture (AGJV) has used on this project, reached the town of Ski on Tuesday 26 February, completing the TBM drilling work. The other two tunnel boring machines completed their work in September last year.
The four machines, each one 150 metres 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 Follo Line 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 the TBM front-end penetrate the rock and the excavated material is then carried 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 has worked extremely hard of which we are proud, delivering quality, safety, innovation and experience. We have excavated more than 18 kilometres 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”, said AGJV project manager, Fernando Vara.
Once the excavation work of the tunnels has been completed, AGJV will carry out all 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 is the largest transport project carried out in Norway to date. It 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.