The tunnel boring machine (TBM) Wilma has reached a major construction milestone on the H53 Pfons–Brenner section of the Brenner Base Tunnel (BBT), completing approximately 5 km of excavation in the western main tunnel and marking strong progress toward the tunnel’s full breakout.

Wilma, a double-shield TBM with a cutter head diameter of around 10.37 m and a total assembled length of roughly 180 m, began tunnelling northward from the Pfons portal in September 2024. Over an operational period of around 18 months, the machine has now advanced about 70 % of its 7.4 km drive on this bore, with approximately 2.4 km still to be excavated before reaching the neighbouring H41 Sill Gorge–Pfons construction lot.

Wilma’s progress runs in parallel with that of its “twin sister” TBM Olga, which is driving the eastern main tunnel on the same section and has already passed a significant portion of its route northwards. Both machines form the final mechanised excavators on the Austrian side of the cross-Alpine project and will together complete roughly 15.2 km of main tunnel drives on the Pfons–Brenner lot.

The Pfons–Brenner section forms the southernmost Austrian stretch of the Brenner Base Tunnel before the Italian border and is a critical link in completing the overall tunnel system. Once finished, the Brenner Base Tunnel will extend 64 km beneath the Alps – 55 km of which are the principal base tunnel tubes – making it the longest underground railway link in the world and a cornerstone of the European north–south freight and passenger corridor.

Wilma and Olga are the last of nine TBMs deployed across multiple construction lots on the BBT project, each excavating large-diameter tunnels that will later be equipped with rail infrastructure to support high-speed passenger and freight services.

Progress on the Brenner Base Tunnel has accelerated in recent years, with mechanised drives deep beneath the Alps complemented by conventional drill-and-blast excavations and extensive exploratory tunnelling. While the project’s expected operational opening is now in the early 2030s, later than originally planned, ongoing work across these final sections continues to push toward that target.

Key data:

Tunnel length (base tunnel): 55 km (total system 230 km)

Wilma TBM diameter: ~10.37 m

Excavation completed (Wilma): ~5 km (~70 %)

Remaining tunnel to excavate: ~2.4 km

Operational target: Early 2030s

For further information please visit the tunnelbuilder archives click here and here 03/26.