The western main tube of the future Brenner Base Tunnel (BBT), running between Italy and Austria, has been dug all the way from Fortezza to the Sill Gorge near Innsbruck. With the final work carried out, “numerous individual tunnel sections have now been joined to form one continuous main tunnel”, BBT said.
The protagonist of this story was Wilma, the tunnel-boring machine (TBM) that was deployed to dig 7.5 kilometres of tunnel in the H53 Pfons-Brenner lot. This beast, deployed in September 2024, is made up of 80,000 individual components for a total weight of 2,700 tonnes and 180 metres in length.
Excavations almost complete
The completion of the 55-kilometre west tube follows another recent milestone. At the end of July, the Austrian and Italian teams met under the mountain with the destruction of the last rocks separating the two countries. Now, only a short stretch in the east tunnel still remains to be dug.
Highlighting the complexity of this project is the fact that it took over 700 days to complete the excavation. In other words, the TBM excavated around 10 metres per day on average. Still, TBMs are much faster than the traditional blasting method, which usually allows for a daily progress of 5 metres.
TBMs were mostly used in the Italian section. Their advantage is that the lining of the tubes can be installed directly after digging, while the blasting method entails more steps making the process longer. “The tubbing segments, each weighing around ten tonnes, were transported by rail to the construction site via the Wolf rail link and then made ready for installation in the tunnel boring machine”, BBT explained.
A much needed infrastructure
The Brenner Base Tunnel should be ready to welcome its first trains in 2032. Currently, convoys have to run along the historical line, which is one of the steepest in Europe and comes with speed and weight restrictions. The BBT will create a flatter link beneath the Alps, allowing trains to be heavier and travel faster.
Rail freight should significantly benefit from the new infrastructure, as the tunnel is part of the TEN-T Scandinavian-Mediterranean Corridor, running from southern Italy to Sweden and Norway. However, a hiccup remains. Germany does not seem too interested in creating access routes to the BBT before the mid-2040s, 10 years after the tunnel is expected to open.