By rosebell
Creating the first continuous tunnel between Italy and Austria, digging process of the Brenner Base Tunnel exploratory tunnel was completed on 18 September.
The event was witnessed by European commissioner for sustainable transport and tourism Apostolos Tzitzikostas, Italian minister for infrastructure and transport Matteo Salvini, and Austrian minister for climate action, environment, energy, mobility, innovation and technology Peter Hanke.
In order to excavating the 56km-long tunnel which runs almost 1,450m deep in the heart of the Alps, TBM Clio was commissioned in 2008.
Stretching between and beneath the two main railway tunnels, this The exploratory tunnel provides information on rock mass which is due to decrease costs and time for the construction of the main tunnels. Following completion of the BBT, the exploratory tunnel will be essential for drainage, for the installation of technical equipment and for maintenance works.
In the current year all excavation works on the Italian side have been completed and by August, 88% of the BBT excavation was completed.
Out of seven construction sites, three sites are active: two in Austria and one in Italy. The completed lots are:
- Lot H71 Isarco river underpass: completed in December 2023. This connects the base tunnel with the existing Brenner railway line and the Fortezza station. Overall, 4.5km of main tunnels and 1.2km of interconnecting tunnels to the existing railway line were built.
- Lot H52 Hochstegen: completed in December 2023. Excavated 4.8km for the exploratory tunnel, main tunnels, connecting tunnels and cross-passages.
- Lot H33 Tulfes-Pfons: completed in September 2021. Excavated 43.3km for the emergency tunnel, main tunnel tubes and exploratory tunnel.
- Lot H21 Sill Gorge completed in December 2024. Connects the northern end of the Brenner Base Tunnel and the central station in Innsbruck.
The three active sites are:
- Lot H61 Mules 2-3: works started in 2011 and excavation of the main tunnel and exploratory was completed in August 2025. In total, 65km were excavated for the main tunnels, exploratory tunnel, cross-cut and access tunnel. All the excavation activities of the BBT on the Italian side have been completed. Final lining is ongoing.
- Lot H41 Sill Gorge-Pfons: works have been ongoing since January 2022. In total, 22.5km of main tunnel tubes and 38 cross-passages with a total length of 2.3km will be excavated. TBMs Ida and Lilia have excavated more than half of the planned tunnel stretches.
- Lot H53 Pfons-Brenner: works started in May 2023. TBMs Wilma and Olga will drive a stretch of 7.6km (a total of 15.2km) in each main tunnel tube. The TBMs started excavating northwards in September 2024. The lot is expected to excavate 25.2km of main tunnel, 1.6km of exploratory tunnel and 2.6km of cross-passages.
As the world’s longest underground railway tunnel, the 64km-long BBT with slopes of only 4-7% runs 580m below the Brenner Pass. The tunnel is going to reduce the Fortezza–Innsbruck line by 20km.
While the new line will link to Fortezza via two single-track tunnels to the south, to the north, it will link to the Innsbruck bypass and the lower Inn valley railway, as well as to Innsbruck railway station.
