Tunnel boring machine (TBM) manufacturer Herrenknecht has released a series of images of the double breakthrough on Norway’s Follo Line rail tunnel last month.
Breakthrough of the two TBMs at Oslo Central Station was live streamed to 25,000 viewers around the world but the new images show key moments of the tunnelling milestone in more detail.
As part of Norway’s biggest rail project, the TBMs have each bored 18.5km of tunnel between the cities of Oslo and Ski. Each tunnel has an 8.8m diameter and has been bored through rock by four double shield tunnel boring machines.
The event was a historic moment for Norway as well as client Bane Nor and joint venture contractor Acciona Ghella, as the use of four TBMs was a first for the country’s tunneling industry where drill and blast is commonly used.
Bane Nor project manager Anne Kathrine Kalager said: “In future TBMs will be a realistic alternative in large projects, even in our extreme hard rock.”
The TBMs were launched in 2016 and have bored over 90% of the 20km tunnels through hard gneiss.
Acciona Ghella selected the double shield TBMs, which combine the principles of gripper and single shield TBMs in one machine, to cope with the hard ground conditions.