The final breakthrough has been made on the main tubes of the Brenner Base Tunnel – a milestone connecting Austria and Italy.
The historic moment came when the ARGE H53 consortium of Porr and Marti broke through almost simultaneously in the western and eastern main tunnel tubes of construction Lot H53 Pfons–Brenner. The breakthrough from the Austrian side connects the tunnel sections to the completed main tunnel tubes of the Italian construction Lot H61 Mauls 2–3.
A Webuild-led consortium used two TBMs – Virginia and Flavia – to excavate the Lot H61 Mauls 2-3 tunnels and completed[https://www.tunnelsandtunnelling.com/news/brenner-base-tunnel-excavation-completed-in-italy/?cf-view] tunnelling in May.
The Lot H53 breakthrough occurred approximately 1,408m below the Geigenspitze peak at an altitude of about 794m. At the breakthrough point, the tunnelling crews worked their way through hard rock and in temperatures of around 30 degree C.
The milestone follows the cross-border breakthrough of the exploratory[https://www.tunnelsandtunnelling.com/news/brenner-exploratory-tunnel-makes-first-cross-border-breakthrough/] tunnel in September last year.
Drilling and blasting in section H53 started in March 2024. Depending on the geological conditions, between 2-5m could be excavated per blasting cycle. Up to the breakthrough, approximately 5km of had been driven in the east tunnel and approximately 5.1km in the west tunnel using drill and blasting.
The two main tunnel tubes were constructed simultaneously. Six to eight workers operated around the clock in four shifts for each drive. Porr says precise co-ordination was essential to ensure that both tubes reached the border almost simultaneously. This included the exact surveying of the tunnel axes, the continuous adjustment of the tunnelling speed to the geological conditions, and co-ordinated planning of personnel, machinery, and materials.
Over the entire tunnelling length of more than 5km, the permitted deviation from the planned tunnel axis was only a few centimetres.
ARGE H53’s TBMs Olga and Wilma – the last of the nine TBMs deployed on the Brenner Base Tunnel – are still at work on the main tunnel tubes towards Innsbruck.
Porr CEO Karl-Heinz Strauss praised the teams’ performance.
“A significant moment like this is the result of dedication, expertise, and team spirit. Our employees have achieved extraordinary things under challenging conditions. Working closely with all project stakeholders, we have already accomplished a tremendous amount, while important tasks still lie ahead. Today we celebrate this success and look back with pride on our own achievement,” he said.
BBT-SE said the event not only marked the completion of two tunnel sections, but also the convergence of two construction sites that had worked independently for several years.
It also said the use of TBMs on the Italian side, and conventional methods and drill-and-blast techniques on the Austrian side showcased two proven tunnelling methods.
The 64km Brenner Base Tunnel will be the world’s longest rail tunnel. It will connect the cities of Fortezza in Italy and Innsbruck in Austria. Passenger trains will travel at speeds of up to 250km/h, cutting travel time from the current 80 minutes to 25 minutes.
