Powerful electric motors with a high total output slowly rotate the head. At the rear of the boring head are hydraulic presses which exert high pressure to push the TBM drilling head against the wall of the tunnel. Under the high pressure of the roller bits, the rock splinters into small pieces, called chips. Directly behind the boring head, the rock is secured to protect the workforce using rock anchors. Depending on the quality of the rock, additional steel arches or other safety measures are incorporated.
Robot arms apply the sprayed concrete.
This material, also known as gunite, lines the arch efficiently and provides the essential protective shield for the tunnel. The excavated material is transported by conveyor to the rear part of the tunnel boring machine. From here, a tunnel railway takes it to the portal of the tunnel, into a buffer silo and to the loading point. Given favourable geology, the TBM can advance up to 50 metres per working day. Because of the complex conditions, the average in the Kandertal tunnel was 18 metres per working day.