By Ashley Karen
Work has been completed on a “complex and challenging” 5km long section of the Brenner Base Tunnel in Austria – getting the megaproject one step closer to a cross-border breakthrough.
The tunnel on construction lot H52 Hochstegen, near the Brenner border, operates through the “Hochstegen zone” – a fault zone characterized by excessively complex geological conditions, which cross from Graubünden slate to central gneiss.
In December 2021, Swietelsky Tunnelbau received the €102M (£88M) contract for this intricate construction lot. It began work on the lot at the start of 2022.
Because of the water-bearing presence and carbonate rock layers, the contractor faced considerable challenges with the excavating in this section. In the direction of the Brenner, approximately 900m of exploratory tunnels had to be bored.
However, the project team encountered a Triassic zone and Hochstegen marble in the exploratory and main tunnel.
Due to the mentioned intense geological conditions, extensive injections, and safety measures should be carried out over the tunnel’s 23-month construction period to enable safe excavation of the structure.
A total of 5km of the tunnel has been blasted, of which 3.2km is the main tunnel, 0.9km is the connecting tunnels, and 0.9km is the exploratory tunnels.
In addition, work on the section has concerned the construction of three branch caverns and two connecting tunnels at the main tunnel level. In total, 400,000m³ of material has been drilled and blasted, and 4,000m³ of grout has been injected during the lot’s construction.
Michael Knapp, the Brenner Base Tunnel (BBT) project manager for the Pfons-Brenner stretch, mentioned: “Despite the technically challenging geology, we got it done within the specified construction time.”
He added: “Thanks go to the responsible construction company and, above all, to the miners who did a great job under these difficult tunnel construction conditions.”
The lot H52 Hochstegen completion gets the megaproject one step closer to a cross-border breakthrough as the exploration tunnel on the lot is just 2km away from the Italian border.
Once the tunnel breaks through from Austria into Italy, it is said to link the two countries for the first time – discovering the ultimate purpose of the project, which intends to connect Italy with Austria through a 64km long railway tunnel.
When finished, the tunnel, commissioned by Brenner Base Tunnel Societas Europaea (BBT SE), is claimed to be the longest in the world, linking Fortezza with Innsbruck.
Construction work was also recently finished on construction lot H71 Eisackunterquerung in South Tyrol, which BBT SE conveyed was also a significantly complex and challenging lot.
Following these prominent project milestones, attention now turns to the construction of the next lot, H53 Pfons-Brenner. It includes 25.2km of the main tunnel, making it the most extensive construction lot in Austrian history.
Nevertheless, in April this year, a consortium including Porr Bau, Marti, and Marti Tunnel was granted the €959M (£844M) contract to construct the tunnel’s Pfons-Brenner section.
