Page 10 - TunnelTalk Annual Review 2014

Fig 2. Plan of works at the Mauls adit junction with the main Baseline Tunnels
Left: Early advance of the exploratory tunnel from Aicha to Mauls by a Seli TBM Right: Earlier drill+blast work at the Wolf adit
Works are also underway at the Wolf adit junction and at the Patsch ventilation shaft near Ahrental.
The main part of the Base Tunnel is 55km long between the Innsbruck and Fortezza portals. Including the existing bypass tunnel of about 9km long, the overall length of the main route infrastructure on the scheme is 64km. This constitutes the longest underground railway connection in the world, said BBT-SE. While freight trains will run at up to 120km/hr through the link, passenger trains will travel at up to 250km/hr.
Due to geological data from the early and exploratory works, especially at the Innsbruck end, it is now expected that most tunnel excavation could be by TBM with spoil removed via the advanced exploratory tunnel, said Lochmann.
The schedule for procurement of two of the three remaining major lots in 2016 and of the third lot in 2018-19 is slightly later than anticipated back in early 2011. At that time, it was expected that tendering for these packages would start in 2015 for construction to begin in 2016. The project completion date is unchanged however, and a nudge upwards in cost is nominal due to the base year shift in published estimates.
The project is a transportation priority for the European Union, and while Austria and Italy are each funding 30% of the scheme, the majority of the 40% balance is being met by the EU. The project is to be completed in 2025 for operational services to begin by late 2026. As part of the key Berlin-Bologna rail transport corridor in Europe’s expanding rail transportation network, the Brenner Base Tunnel will eliminate the steep grades of the existing Brenner railway built in the 1860s. n
References
• Brenner Base Tunnel – let the works begin! – TunnelTalk, April 2011
• Brenner project takes a major leap forward – TunnelTalk, February 2011
• Exploratory bore for Brenner Baseline through – TunnelTalk, November 2010
• Design consideration on approach to Brenner Baseline high-speed rail connection in Austria – TunnelTalk, February 2008
Impregilo JV plans to use a 7.9m diameter TBM to drive southwards from the Ahrental junction towards the Wolf adit zone. When the new stretch is completed, just more than half of the exploratory tunnel will have been excavated. At the Ahrental adit and junction, the JV will add short drill+blast extensions to the main tunnel headings.
The other works in the Tulfes-Pfons Lot relate to creating a link off the base tunnel to connect to the heart of Innsbruck. Two connecting tunnels will link the Base Tunnel with the existing, single tube trans- Alpine rail freight tunnel that bypasses the city of Innsbruck.
The bypass connecting tunnels will be larger than standard of running tunnels, explained Lochmann. “BBT-SE, as designer of the scheme, said the different alignments of the connecting tunnels, sweeping either over or under the alignment of the main Base Tunnels, prevents them from being linked by cross passages. As a result, and to provide safe zones along this stretch of the scheme, the tunnels are designed with a cross section of about 120m2, and will have a concrete dividing wall to create the necessary safety zones.”
Once the link tunnels merge with the rail bypass tunnel, and to prepare to carry passenger trains as well as freight trains, the existing tunnel will also need safety improvements. The design solution is for the safety/rescue tunnel to run parallel to the bypass tunnel. The safety tunnel will have a cross section of 35m2 that will allow vehicles to pass, said BBT-SE in a statement. Excavation of this tunnel
will progress from the Tulfes and Ampass access adits.
Other works underway at mid- 2014 for the project included extending the exploratory tunnel northwards by drill+blast from the Mauls (Mules) junction. Undertaken by a JV of Oberosler, PAC and Implenia, the work includes excavation of TBM launch chambers for future lots, and a short advance of the main running tunnels (Fig 2). The drill+blast headings are in the project’s largest identified fault zone, the Periadriatic Seam, which is a tectonic plate boundary.
Groundbreaking ceremony in September 2014 on the Tulfes–Pfons section of the River Eisack undercrossing
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TunnelTalk AnnuAl Review 2014 www.TunnelTalk.com
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