Norwegian Prime Minister Jonas Gahr Støre, Transport Minister Jon-Ivar Nygård and the CEO of Bane NOR Gorm Frimannslund boarded the first train of the Follo Line (Folloban) together with King Harald V of Norway and Crown Prince Haakon Magnus. The 22km long double track connects Oslo Central Station with the transport hub at Ski Station in just 11 minutes.
The longest twin tube tunnel in Scandinavia
This record travel time, which halves the time previously required, is made possible by the use of the 19km twin-tube tunnel named the Blix Tunnel, the longest twin-tube tunnel built in Scandinavia. With this new high-speed link (250km/h), the Norwegian rail network is further strengthened, which should encourage a modal shift from road to rail.
SYSTRA SWS was in charge of engineering services (Detail Design, Construction Supervision and As-built) for two sensitive lots in the Follo Line project: the cut-and-cover tunnel between Oslo Central Station and Ekebergåsen, and the 1.3km drill & blast excavation required to approach the tunnel boring machine (TBM) starting chainage.
We are proud to have been involved in the design of Norway’s largest transport project to date. There have been many challenges, from ground investigation/condition to construction supervision, always with the aim of minimising environmental and social impacts and with no disruption to ongoing traffic. Congratulations to all the teams involved in this historic project!Federico Eccel, Project Director, SYSTRA SWS
SYSTRA SWS underground expertise
The project involves the excavation of the three main tunnels with the adoption of the Drill & Blast excavation method. Below are some data on the tunnels:
- 2 tunnels for the new Follo Line (section 90m2)
- 1 tunnel for the Østfold Line connection (section 95m2)
- 1 three-track cave (section over 300m2)
- Link and access tunnels (section 37m2)
Excavation by Drill & Blast was made complex by the presence of numerous underground networks (metro tunnels, pipes, oil tanks, etc.), which were taken into account during the design phase, carried out with Strand7 FEM software.
In areas with low rock cover, another excavation method was used for the first time in Norway: Drill & Split. Compared to the use of explosives, this method minimises the effects of vibrations and subsoil deformation.
Photo credits: Bane NOR.