The contract includes the design and construction, through an EPC, of twin tunnels with an internal diameter of 8.8 m, performed with 4 tunnelling machines, each measuring 19.5 km long.
Once completed, the twin tunnels – designed for high-speed trains reaching up to 250km/h – will link the cities of Oslo and Ski and will be the longest railway tunnels in Scandinavia. They are being excavated by four huge, double shield tunnel boring machines (TBMs).
The work consists of the largest, and second largest, of four EPC turnkey contracts included in the Follo Line project, Norway’s biggest transport infrastructure project to date.
The TBMs started work halfway through the section, where the facilities serving the casting and concrete plants are located. Access to this area, where an escape tunnel and two caverns for the assembly of the TBMs have been installed, is through a series of drilled and blasted tunnels. The 40cm-thick lining of the tunnels is made up of almost 20,300 pre-fabricated rings, each comprising 7 segments.
The works performed with the tunnelling machines start in the middle of the route, where the facilities serving the keystones and concrete plants are located. Access to this area, where a rescue area and two caverns for the assembly of the tunnelling machines have been installed, is carried out through a series of tunnels built by digging and blasting. The tunnel’s lining is composed of around 20,300 prefabricated rings, with seven keystones each, measuring 40 cm thick.
ACCIONA in JV with Ghella has been working hard to mobilise the Follo Line Rail project since its award in March 2015. The four TBMs are now on site and are currently being assembled to commence tunnel boring. These specially designed TBMs will have an average excavation speed of 12-15 m/day.