Construction site “H41 Sill-Pfons Gorge”: TBM Ida is about to enter a large fault zone

After a 2024 marked by significant milestones, 2025 begins with a new challenge for the H41 Sill Gorge-Pfons construction site, the northernmost active construction lot of the BBT project.

The two TBMs working on the H41 Sill Gorge-Pfons site, Lilia and Ida, each completed 5 km of excavation in 2024 and are now less than 3 km away from their final destination in the municipality of Navis. This remarkable progress, which began in May and June 2023 respectively, might suggest that their path has been straightforward, but that is far from the case. The achievements of the past year and a half are all the more remarkable given the challenges that have been overcome. The route for both TBMs has been, and will continue to be, very demanding. Both TBMs have already crossed two major fault zones, named "Viggartal" and "Walzn".

In a few days' time, TBM Ida, which is currently working on the main west tunnel, will face a new challenge: the "Werner" fault zone, located below the Arztal valley in the town of Pfons. "The experience gained during the excavation of the exploratory tunnel has enabled us to identify an area of highly fractured and unstable rock. To ensure safe progress, the machine's speed will be reduced in the next few days to allow consolidation work to be carried out", explains Ivan Zamberlan, lot controller at the "H41 Sill Gorge-Pfons" construction site.

In about a month, TBM Lilia will encounter a similar section in the eastern main tunnel. Crossing the fault zone will require a reduction in speed to allow the necessary consolidation work to be carried out safely.

Meanwhile, the final concrete lining work continues in the completed tunnel sections, with about a quarter of the planned lining in the main tunnels northwards already completed.

The year 2025 promises to be a pivotal one for the H41 Sill Gorge-Pfons construction site, marked by significant technical challenges. Here, a stone's throw from Innsbruck, innovation, safety and sustainability are intertwined, making every step forward a decisive move towards the completion of an infrastructure that will revolutionise European mobility.