Brenner Base Tunnel exploratory tunnel Ahrental‐Pfons – interaction between tunnel boring machine and rock mass as well as measures to manage fault zones

Approx. 42 km of tunnel were excavated on the contract Tulfes‐Pfons H33, including a 15 km long section of the exploratory tunnel, which has been excavated since October 2015 with a gripper TBM from the Ahrental access tunnel southward into the district of Steinach. The interaction of the tunnel boring machine with the rock mass is discussed here as a back analysis of the mechanized tunnelling drive. This article does compare the forecast with the actual geological/geotechnical conditions, but only considers the conditions actually encountered. The back analysis takes place analogously to the principle of geotechnical planning according to the ÖGG (Austrian Society of Geomechanics) guideline, in which, starting from the rock mass structure and the rock mass types, the encountered tunnel face and intrados behaviour are observed and an estimation of the system behaviour is carried out. A description of the tunnelling technology concept completes this paper together with two case studies and the lessons learned.