In the TBM (Tunnel Boring Machine) section of the Follobanen project, ACCIONA collaborated with the Italian company Ghella 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 between ACCIONA and Ghella 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.
KEY ASPECTS
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 between ACCIONA and Ghella 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.
GENERAL INFORMATION
- Location: Oslo, Norway
- Contract type: EPC (Engineering, Procurement, and Construction)
- Infrastructure: Dual-bore railway tunnel, each bore 18.5 km long with an internal diameter of 8.75 meters, excavated through rock using four double-shield TBMs.
- Project delivery: 2023
- Objective: To halve travel time between Oslo and Ski from 22 to 11 minutes.
- Benefit: Economic development in the region and improved communication between Oslo and Ski.
- Milestone: Upon completion, this became the longest railway tunnel in the Nordic region.
ENVIRONMENTAL IMPACT MANAGEMENT
One of the priorities of the AGJV consortium whilst the project is being carried out has been to minimise the environmental impact.
- AGJV used conveyor belts to move rock debris to the workplace in Åsland and eliminated the need for thousands of vehicle trips to complete the same task, avoiding the emission of more than 27,000 tonnes of CO2 during tunnel drilling.
- AGJV has reused 75 % of the excavation material for the preparation of the so-called deposit area where Oslo City Council will subsequently undertake urban development.
- In collaboration with ACCIONA, a complex tunnel water treatment system was designed that includes the addition of ferrous sulphate to the circuit, allowing the management of incoming water from the simultaneous excavation of 4 TBMs, with a discharge of approximately 200-250 m3/h, high pH and TSS values as well as high hexavalent chromium (CrVI) content. The chromium action plan implemented in the WTP has allowed the reduction of CrVI by 75 %. The treatment of water in the project has also allowed the reuse of water (more than 80 %) in work activities, minimising the consumption of natural resources.
- Monitoring is carried out in order to meet both ACCIONA and the client's sustainability requirements during the execution of the work. This monitors, among other aspects, the consumption of energy and materials, prioritising the use of materials with EPD (developing it where necessary, in collaboration with ACCIONA's R&D department), certified timbers and using machinery with high environmental standards.
Project implementation complies with all of Norway's strict environmental laws and regulations, as well as with the corporate objectives of the National Railway Administration of Norway.