The construction of Eisack River underpass of the Brenner Base Tunnel has been completed by the consortium of companies led by Webuild and including Strabag, Collini Lavori and Consorzio Integra.
Following the completion of the construction work for the future railway tunnels, the site will be cleared and the areas will be greened in a manner compatible with the seasonality of the tree species.
The Eisack underpass lot H71 constitutes the southernmost part of the Brenner Base Tunnel, before the access to the Fortezza station. The lot has involved the excavation of approximately 6 km of tunnels running for a total of 240 metres under the bed of the Eisack River. Innovative, state of the art technology was used in its construction. For the Eisack River underpass, one of the most complex sections, the technique of ground consolidation by freezing was adopted, allowing the construction of tunnels where there is a strong presence of groundwater and in full respect of the environment, preserving flora and fauna.
The freezing technique, which comes before the excavation phase, ensures the freezing of a portion of soil, between the tunnel to be excavated and the river above, sufficient to make the excavation impermeable to water and ensuring stability. Its application involves a pre-consolidation phase, in which the soil is drilled into the section below the river and its permeability is reduced by cement injections. Next, there is the freezing phase, with the introduction of liquid nitrogen at a temperature of around 196 degrees Celsius below zero: the cooling liquid circulates in the holes made around the excavation perimeter to create a one-metre thick shell. The last stage is where the ice shell is maintained by the use of brine brought to a temperature of between 30°C and 35°C below zero.
The Eisack River underpass (lot H71) will contribute to the completion of the Brenner Base Tunnel, which is among the most strategic sustainable mobility projects that Italy is investing in.
On the Italian side, in addition to the Eisack underpass lot, the Mules 2-3 lot is being constructed with the Ghella Group. On the Austrian side, it is carrying out work on the Sill – Pfons Gorge lot and has already completed the Tulfes – Pfons lot. In addition to these lots, there are the works for the Fortezza – Ponte Gardena high-capacity line and the Trento railway bypass, for the connection of the line to Fortezza and Trento, respectively.
The Brenner Base Tunnel will connect Fortezza, in Italy, to Innsbruck, in Austria. With a total length of 55 km, 64 km if the existing Innsbruck railway bypass is included. When completed, the tunnel will reduce travel time from Fortezza to Innsbruck to 25 minutes for passenger trains, from 80 minutes, and for freight trains to 35 minutes from 105 minutes currently.
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