Brenner Base Tunnel Reaches Project Milestone
At the end of last month, international infrastructure firm Webuild Group announced that its tunnel boring machine, named “Serena,” has completed the exploratory tunnel for the Brenner Base Tunnel. The TBM excavated more than 14 kilometers (about 8 miles) over three and a half years.
The milestone brings the excavation of Lot Mules 2-3, which is the largest site of the project, to 82% completion. The ongoing construction effort to build new rail tunnels through the Alps from Italy to Austria is reportedly valued at 8.8 billion euros (almost $10 billion) and is expected to be the longest railway tunnel in the world.
The tunnel will be part of the Scandinavian-Mediterranean Corridor of the Trans-European Transport Network, reducing travel times by 69% from 80 to 25 minutes.
“Today’s event fills us with pride because, with this work on the Brenner, we are contributing to the construction of one of the most challenging sustainable and engineering projects in the world. This project is also thanks to Progetto Italia, the industrial operation that had Webuild take over Astaldi, that was undergoing a composition with creditors procedure,” said Webuild General Manager Global Operations Claudio Lautizi and Director Domestic Operations Nicola Meistro in a statement.
“This guaranteed the completion of a project that is strategic for all of Europe. It also safeguarded jobs. A special thanks to the workers who allowed the work to go ahead despite the many complications, applying the most rigorous safety standards.
#BrennerBaseTunnel Lot Mules 2-3: 82% excavation completed! #TBM “Serena” arrived at #Brenner after excavating more than 14Km. New milestone for the Brenner Base Tunnel, #sustainable megaproject that will connect Italy and Austria under the #Alps#Webuildhttps://t.co/khMTfGma2k pic.twitter.com/BZTskjhKAh— Webuild (@Webuild_Group) November 26, 2021
“Today, Italy is going through an exceptionally active period for the planning and construction of infrastructure projects. We need to take advantage of it, moving towards a virtuous collaboration between the public and private sectors. It is something that we successfully experimented with it on the construction of the Genova San Giorgio Bridge. It should be applied elsewhere in the country, starting with this project.”
Now that Serena has completed its job, Webuild plans to dismantle the TBM inside the tunnel. The company reports that Serene “majestically” dug through at least four kilometers (about 2.5 miles) of rock every year, with 2,800 kilowatts of driving power, despite obstacles from the COVID-19 pandemic.
Webuild BBT Involvement
The company holds four contracts for the BBT:
According to reports, Webuild took over the contract for Lot Mules 2-3, which was worth $1.1 billion at the time of the award in 2016. In late 2020, Webuild acquired 65% of the original contractor company, Astaldi.
Lot Mules and the Isarco River Underpass are currently under construction, while the Tulfes-Pfons lots was completed.
In November, Webuild announced that it and its Swiss subsidiary SCS won the Lot H41 Gola del Sill-Pfons of the BBT. The project is reportedly valued at 651 million euros (about $734 million) and is a joint venture with Swiss partner Implenia.
The contract consists of the construction of a railway from Gola del Sill near Innsbruck to Pfons, including traditional excavation for the two parallel tunnels running 7.3 kilometers (4.5 miles) and mechanized excavation for another 16.5 kilometers (10 miles). Webuild will also line the walls of completed tunnels, an emergency stop at Innsbruck, access tunnels, exploratory tunnels and parts of other secondary tunnels.
About the Project
According to reports, the BBT is a straight, flat railway tunnel connecting the two European countries Austria and Italy. Once completed, the tunnel will expand 55 kilometers (34 miles) between Innsbruck, Austria portal and Fortezza, Italy portal through the Alps.
However, after connecting the Innsbruck bypass (the Inn Valley Tunnel which opened in May 1994) to Fortezza, the tunnel will stretch 64 km, making it the longest railway tunnel in the world.
“This tunnel is a masterpiece along the North-South-Corridor (Scan-Med-Corridor) in Europe, belonging to the TEN (Trans-European Network for transport, energy and telecommunications) of the European Union,” explained Konrad Bergmeister, CEO of Brenner Base Tunnel SE. “The tunnel itself has a very high relevance for the three European countries Germany, Austria and Italy since the Scan-Med-Corridor with a total length of 9,000 km – starting in Finland, running through the three countries and ending at the island of Malta – is the longest of the nine Trans European Network corridors connecting all parts of Europe.”
The system is comprised of two main tubes, each 8.1 meters wide (26.6 feet wide), running 40-70 meters apart from one another. Inside, the tubes will be equipped with a single track for one-way train traffic. In the event of an emergency, the tunnels are designed to have three emergency stopping areas. The two tubes are also connected to one another every 333 meters.
The construction lot “Periadriatic seam,” was carried out between October 2011 and Summer 2015, and comprised the excavation of 3.7 km of the main tubes and 1.5 km of the exploratory tunnel.
In the summer of 2014, the Tulfes-Pfons lot in Austria, worth 380 million euros (about $461 million), was awarded to the Strabag/Salini Impregilo bidding consortium, with excavation work following that fall. Work for this portion of the project was slated to reach completion by spring 2019.
“The construction lot includes about 40 km of tunnel excavation with Tulfes emergency tunnel, Innsbruck emergency stop, main tunnel tubes, connecting tunnels and the Ahrental-Pfons exploratory tunnel,” explained TBM manager Sebastian Grüllich from Strabag, the technical leading company. “About 25 km of that, we excavate with drill-and-blast and 15 km with mechanized tunneling. The excavated volume will be about 2.3 million m3 and about 430,000 m3 structural concrete for the inner lining will be used.”
In May 2016, Mules 2 to 3 were awarded to bidding consortium Astaldi S.p.A., Ghella S.p.A., Oberosler Cav Pietro S.r.l., Cogeis S.p.A. and PAC S.p.A a contract worth 993 million euros. Construction on this portion of the project launched that following September and involves the construction of 65 km of tunnels, 39.8 km of main tunnels, 14.8 km of exploratory tunnels, in addition to various access and emergency stop tunnels.
In 2018, BBT signed a contract with Porr, Hinteregger, Condotte and Itinera for the Pfons-Brenner section in Itlay. However, this contract was terminated in October of last year. BBT is currently reassessing and optimizing the section for another tender.
Another recent update, last year, main contractor Porr Bau started work on the H21 contract in August. The Sill Gorge site in Austria involves constructing the link between the Brenner Base Tunnel and the central station in Innsbruck and will involve 600 meters of tunneling as well as the construction of three major bridges. Work is slated to complete in 2024.
Taking place at the Mules 2-3 section, in March a Herrenknecht tunnel boring machine set the record of boring and lining an 860-meter-long tunnel in just one month. The TBM, named Virginia, is a 10.65-meter diameter double shield. The record was achieved after the TBM was noted to have developed an average advance rate of 27.7 meter per day during the month with a daily best performance of 36.75 meters.
At the time, BTC was utilizing three Herrenknecht TBMs for the project.
In achieving the record, Herrenknecht credited the stable geology, a mixture of carbonate and limestone schists, along with the capacity of the double shield TBM.
Major progress was also made on the tunnel below the Isarco river with breakthrough on the 57-meter section. The work was completed in just one month following use of ground freezing techniques to avoid the need to re-route the river.
Work there was being delivered by the Isarco joint venture formed by Webuild, Strabag, Consorzio Integra and Collini Lavori and will link Brenner Base Tunnel with the existing Brenner line and the railway station in Fortezza.
Work on the Mules 2-3 section was expected to reach completion by 2023.
Due to the fact that the European Union considers the Brenner Base Tunnel a high priority infrastructure project, 50% of the costs for the exploratory tunnel and 40% of the costs for both main tunnels are being financed separately. The remaining 50-60% of the costs will be covered by Austria and Italy each. Specifically, the BBT is being financed under the budget of the Trans-European Networks with support from the EU.
The BBT is expected to reach full completion by 2026.