Oslo Follo Line/ Norway – Project Challenges and TBM Solutions
Until recently, all rail tunnels in Norway were excavated using drill & blast technology. The Follo Line project is a new 22 kilometers long double track rail line that is currently under construction between Oslo Central Station and Ski. Four double shield hard rock TBMs with an excavation diameter of 9.96 meters excavate a total of about 36 kilometers of predominantly Precambrian gneisses with banding and lenses of amphibolite and pegmatite. The tunnelling concept is based on using four TBMs, two of each operating in opposite directions from two access tunnels that are located near the midpoint of the alignment in a remote, rural location. When finished, the tunnel will be Norway’s longest and largest rail tunnel. The paper highlights the project challenges in particular the abrasive and strong rock mass, the large diameter in combination with the possible risk of high water pressures (12 bar) that require a well-adapted TBM concept.