ITALIAN State Railways’ (FS) engineering consultancy Italferr has announced the successful completion of tunnelling work under the Isarco river as part of the project to build the new Brenner Base Tunnel connecting Italy and Austria.

As the leader of a joint venture also including Pini Group and Hbpm Ingegneri, Italferr has been responsible for managing civil engineering work undertaken by a separate joint venture led by Webuild.

Italferr says that local geological conditions, as well as the presence of the Brenner Motorway, the SS12 highway and the existing railway between Verona and the Austrian border, required a highly technical design solution.

To safely excavate four 60m single-track tunnels under the river, including two bores to connect the base tunnel with the existing network at Fortezza station, special probes were driven into the ground, which was then frozen during the first phase using liquid nitrogen at a temperature of -196°C. During the subsequent maintenance phase, this was replaced by a saline solution cooled to -35°C.

Freezing the water in the ground around the tunnel created an impermeable and resistant shell, enabling excavation to be carried out using traditional methods.

Italferr says that completion of this work marks an important step forward in the construction of the 64km Brenner Base Tunnel, which when it opens in 2032 will become the longest railway tunnel in the world.

Completion is expected to cut journey times by 69% and increase freight capacity by 50% on the Verona - Innsbruck route, forming part of TEN-T Core Corridor 5 connecting the Mediterranean with Scandinavia.

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