Lining segment production for the Brenner Base Tunnel is ending at the Isocell factory in Hinterrigger. And TBM Flavia has almost reached the finish line

The factory just outside Brixen has produced almost 26,000 rings and more than 38,000 base segments for the stretches of the main tunnels and the exploratory tunnel for the Mules 2-3 lot of the Brenner Base Tunnel. And now production work continues, serving the Fortezza-Ponte Gardena section of the southern access route to the future longest railway tunnel in the world.

 

On 13 December 2017, production of the segments started at the Isocell plant in Hinterrigger. This is a virtuous example of how excavated material can be efficiently and sustainably reused, in this case to produce the precast concrete elements for the final lining of the Brenner Base Tunnel tunnels. Approximately 30 per cent of the spoil excavated in the Mules 2-3 plot was used for the production of tubbing rings.

 

It was a massive undertaking, noted Alessandro Marottoli, Project Manager for the ‘H61 Mules 2-3’ construction lot: “From 13 December 2017 to 19 September 2024, when the production of Hinterrigger tubbing rings for the BBT ended, 16,285 rings and 16,298 base tubbing rings were produced for the main tunnels, as well as 9,456 rings and 21,762 base tubbing rings for the exploratory tunnel."

 

Each ring consists of seven tubbing segments plus a base segment in the main tunnels and two base segments for the exploratory tunnel. In total, 218,247 tubbing rings were produced in Hinterrigger for the Brenner Base Tunnel. Each tubbing ring for the main tunnel weighs nine tonnes on average, whereas the tubbing rings for the exploratory tunnel weigh only half as much.

 

From Hinterrigger to the Brenner Base Tunnel

 

So, we’re talking about over 200,000 tubbing rings. But where do these precast concrete lining elements go? Three TBMs at the Mules site have excavated - or are still excavating - the two main tunnels and the exploratory tunnel: Serena, Flavia and Virginia. The TBMs dig deep into the heart of the mountain, but they also assemble and install the tubbing rings which form the final lining of the tunnels.

 

And another important detail: these tonnes and tonnes of concrete are not transported via lorry to the construction site, but by rail, in special trains that travel to the TBMs that will then complete the lining of the tunnel. Each train can carry 2 rings, for a total of 14 elements. This avoids congesting local traffic on the SS12 and is an environmentally sustainable solution.

 

Previously, on our Brenner Base Tunnel TBMs... Serena started in May 2018 and reached the Brenner Pass on 24 November 2021, after excavating 14 km of the exploratory tunnel. Virginia started work exactly one year after Serena, in May 2019, and also travelled 14 km, arriving at the Austrian-Italian border on 28 March 2023.

 

Virginia’s twin sister, Flavia, was launched in April 2019 and is still on her way, but her finish line is in sight: about a mile separates her from the state border today. In the meantime, the tubbing ring factory in Hinterrigger is still operational: the production of precast concrete elements for the Fortezza-Ponte Gardena section, an important part of the southern access route to the Brenner Base Tunnel, continues.

 

Hinterrigger, with its re-use of around 30 per cent of excavated spoil, is a clear and efficient example of a circular economy. And it is also a further demonstration of how the Brenner Base Tunnel will, in the future, be a concrete alternative to road transport, having taken great care to respect the natural environment in the project area during the construction process.