For the construction of the tunnel, Herrenknecht delivered a gripper TBM, which the company notes is specialised in fast tunnelling in hard rock. The tunnelling team made advances of up to 322m per week and 72m per day was excavated with a route gradient of 4.8 per cent. The TBM excavated through Phylite slate, quartzite, limestone mica slate and green slate with carboniferous banded limestone.
Only five and a half months after the start of tunnelling at the end of March 2013, the miners of Switzerland-based Marti Tunnelbau construction company celebrated the successful breakthrough late last year.
