PROJECT | ROCK TUNNELS
CONNECTING TUNNEL H33 - Tulfes to Pfons Off-line from the main Brenner Base Tunnel, the Connecting Tunnel is, as noted, vital to the TEN-T high- speed rail corridor that passes Innsbruck. It is tied-in to the Brenner Base Tunnel and the necessary and complex package of tunnel works involved have been executed under contract Lot H33. The H33 package has taken an existing, wide,
bypass rail tunnel and alongside built a parallel tube (emergency tunnel), and linked them with cross passages. In addition, the existing main bypass tube is linked across (via split tunnels) to the main tubes of the Brenner Base Tunnel, in the Ahrental area. The complex Lot also then built most of an Emergency Stop’s large tunnels at Ahrental on the Base Tunnel, and from there also bored south a portion of the exploratory tunnel. The contractor was a JV of Strabag and Webuild
(formerly Salini-Impregilo), which was awarded the works in mid-2014. By Q3-2021 the excavations in the package of underground works had been completed, involving a total of 43.3km of tunnels. While Brenner Base Tunnel has two main tubes, the
Connecting Tunnel will take both lines of trains in a single tunnel. As such, for emergency support and safety purposes, the parallel 9.7km-long tunnel was needed, of smaller width (35m2
). This is Tulfes Emergency
Tunnel, excavations for which were performed by Drill and Blast method, with three advancing faces: the portal at Tulfes; and, from the Ampass intermediate adit (built previously, over 2011-13, following early exploratory works under Lot 32) from where faces were blasted in opposite directions. The Tulfes Emergency Tunnel was completed in
mid-2017. That Summer also saw completion of the Connecting Tunnel’s tie-in tunnel to the Brenner Base Tunnel, at Ahrental.
The package of works also included a stretch of main
tunnels, along with part of the Innsbruck Emergency Stop large tunnels, as noted, also at Ahrental. At the southern end of the H33 package of tunnelling
works there was a portion of the exploratory tunnel bored southwards from Ahrental towards Pfons, and beyond. This was not the first part of the exploratory tunnel at the north end of the project. Previously, a portion was built at the north end, in the Sill Gorge area, over 2009-2013, and it was constructed south as far as Ahrental. Therefore, the H33 package was extending the exploratory tunnel farther south from Ahrental. The southern extension of the exploratory tunnel was
performed by an approx. 8m-diameter gripper TBM, which bored almost 17km southwards - beyond Pfons and almost to the next Emergency Stop (St Jodok, in Lot H53). It was bored through quartz phyllite and slate, starting in Q3-2015 and finishing in mid-2019. Like the other sections of exploratory tunnel works,
undertaken earlier, the purposes was to gather geological data in advance of the main tunnel works. In this case the works that would come later, at Ahrental and for the main tubes either side of the exploratory tunnel, would be performed in a separate Lot (H41). The TBM met some challenges with collapsing ground that had to be repaired but the works also saw adjacent portions of the main tubes also constructed, ahead of the TBM drives to be done later, on H41.
BRENNER BASE TUNNEL H21 - Sill Gorge & Portals At the north end of the Brenner Base Tunnel, just south of Innsbruck, saw complex works performed and completed for Lot H21 Sill Gorge (Sillschlucht in German, or Gola del Sill in Italian). The mixed package of construction activities included bridges, river engineering works, roads and the Innsbruck Portal structures and initial, some tunnels - up to 130m lengths of the two main tunnels (Viller Berg section), leading to cut-and-cover stretches (Silltal section). The contract was led by Porr Bau. All excavation
works on the lot were completed by mid-2022. Most of the main works on the Lot, though, were above ground and involved a wide range of civil engineering structures over a relatively short distance involved in the narrow gorge, already packed with infrastructure. All works were completed at the end of 2024. It would
be a few months later that the short lengths of main tunnels would see their first connection with a portion of longer main tube tunnel, constructed as part of the neighbouring Lot H41 Sill Gorge-Pfons. Prior to these. Works, though, more extensive
tunnelling works were undertaken in the Sill Gorge area for the Brenner project, focused on excavating the north end of the exploratory tunnel. Excavation of that 5.4km- long portion of the exploratory tunnel began off the main tunnel alignment in late 2009. Construction of the 26m2
tube finished four years later, in late 2013, within the alignment and near Ahrental.
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