Webuild Group press note (I changed the name of the river to Italian).

Webuild: Isarco Underpass Work Completed

Along Construction Site Of World's Longest Underground Rail Link
A Success Story For The Women And Men Of Webuild And The Supply Chain Companies

The Project, Part Of The Brenner Base Tunnel, Was Built With Innovative Cutting-edge Technologies And The Involvement Of A Supply Chain Of 600 Companies

Milan, 10 August 2023 - At the construction site of lot H71 “Isarco River underpass” of the Brenner Base
Tunnel, all the main works have been completed, with the signing of the work completion report. A consortium of companies led by Webuild and including Strabag, Collini Lavori and Consorzio Integra, with the involvement of a supply chain of 600 companies, is engaged in constructing the works. The lot includes an underpass of the Isarco River and will contribute to the completion of the Brenner Base Tunnel, which is among the most strategic sustainable mobility projects that Italy is investing in. 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 Brenner Base Tunnel is a record-breaking tunnel connecting Fortezza, Italy, to Innsbruck, Austria. With a total length of 55 kilometres (64 kilometres if the existing Innsbruck railway bypass is included), it will be the longest underground railway link in the world. It will connect Italy to Austria across the Alps, allowing a significant reduction in travel time. Today, travelling by train from Fortezza to Innsbruck takes 80 minutes for passenger traffic and 105 minutes for freight traffic, while in future, when the tunnel is completed, it will take 25 and 35 minutes, respectively.

The Isarco Underpass lot 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 kilometres of tunnels running for a total of 240 metres under the bed of the Isarco River. Innovative, state of the art technology was used in its construction. For the Isarco 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 Brenner Base Tunnel is an integral part of the Scandinavian-Mediterranean Corridor, a key component of the TEN-T trans-European transport network, and lies on the Munich-Verona axis, where Webuild is currently working on five projects, plus one already completed. On the Italian side, in addition to the Isarco 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.

https://www.webuildgroup.com/en/media/press-notes/webuild-eisack-underpass-work-completed/