Lyon-Turin begins base line tender process 19 Mar 2020

Fig 1. Base tunnel design and main excavation drives

The €8.6 billion cross-border section of the Lyon-Turin rail line runs between Susa in Italy and Saint-Jean-de-Maurienne in France. Of the 65km section, 89% will run underground. The most significant element of the new line is the 57.5km twin-tube tunnel beneath the Mont Cenis mountain range, of which 45km will be in French territory and 12.5km in Italian territory (Fig 1). The Mont Cenis base tunnel will replace the 150-year-old mountain railway that includes the 13.7km single-tube Fréjus rail tunnel, which was opened in 1871 and now fails to meet current safety standards. The new base tunnel will have 204 cross passages at 333m intervals, four intermediate accesses, five central ventilation systems and three underground security areas (Fig 2).

All four of the access tunnels, three in France and one in Italy, have been completed and work began in early 2019 on the artificial tunnel that will be the entrance to the base tunnel on the French side.

Fig 2. Alignment of the railway line and base tunnel

In September 2019, the first of eight TBMs to be used on the project finished excavation of the first 9km of the southern tube of the base tunnel, reaching the La Praz access adit. The 11.25m diameter hard rock single shield TBM started its journey in the summer of 2016 from the Saint-Martin-La-Porte access adit and managed to maintain an average speed of 15-20m/day. This first €390 million lot of the base tunnel was constructed by a joint venture of Batignolles TPCI, Eiffage TP, Ghella, CMC, Cogeis and Sotrabas. Egis and Alpina provided project management.

“The drive encountered several challenges,” said Mauricio Bufalini, Deputy CEO of TELT, the project client. “At about 300m in, the TBM encountered a significant geological fault that stopped excavation for several months.” After crossing the fault, the TBM entered, explored and crossed the Briançonnais Houiller zone, and safely negotiated faults of carbonaceous deposits under overburdens of more than 700m. “The lessons learned from this operation were applied when a similar fault was encountered and crossed in less than one month,” said Bufalini.

New contracts and design

After completing the first contract, TELT launched procurement for the remaining contracts for the cross-border section of the tunnel. Four contracts with a total value of €2.3 billion will be awarded for the remaining main lots between Saint-Jean-de-Maurienne in Savoy, France, and Susa in Piedmont, Italy. Seven further hard rock TBMs will be deployed and will work in parallel to excavate the remainder of the base tunnel.

“The selection committees are currently examining the proposals,” said Bufalini. “We know that more than 100 companies from all over the world are competing for the four main contracts.” The companies are currently preparing proposals for the three French lots with the first due date in April. The Italian lot is still in the earliest stage of the tender process. “We are expecting the next project TBM to be operational by the end of 2021,” Bufalini said. “The goal is to complete all excavations by 2026.” The new railway line, with several additional tunnelled lengths, is expected to be operational in 2030.

Since Bufalini last spoke to TunnelTalk in 2013, security and safety concerns have led to the need to implement drastic changes in the final design of the project. This is particularly related to the main worksite on the Italian side. The main site for base tunnel excavation was originally to be in Susa, but the Italian Government decided to move it to the nearby Chiomonte site, which is connected with the La Maddalena exploratory and access adit.

“La Maddalena will now become the main Italian work site and in December 2019, we awarded a €40 million contract for the construction of 23 interchange 30-40m long x 3m wide niches to facilitate the passage of construction site vehicles in the Maddalena exploratory tunnel,” said Bufalini. The niches will be excavated over a period of 19 months. This will start the transition of the construction site to base tunnel operations.

In addition, the new design included a reversal of the mechanised excavation direction in favour of a downhill path, a reduction of the space available for the main construction site, and a particularly complex logistical setup. The classical design approach has been overturned in order to convert constraints into opportunities for the project, especially for the local regions and the environment.

These opportunities include a reduction in the use of soil, an increase in the proportion of the excavation conducted with TBMs and a wholly underground handling of asbestos-containing rocks.

“The true challenge is to create opportunities for the region and the environment of these projects, subverting if necessary the usual design approaches and insisting, more and more, on sustainable designs so that these projects can be seen and appreciated as positive vehicles for change,” said Bufalini.

As a result of moving the Italian base tunnel worksite and entrance to Chiomonte, the pre-existing worksite needed to be expanded. This impinged on the habitat of the endangered Zerynthia Polyxena butterfly. TELT set up a special environmental protection team to create an ecological corridor that will allow the butterflies to migrate to a forest where conditions are better suited to its survival.

To support sustainability, TELT is determined to recycle 60% of excavated rock to manufacture, among other uses, the concrete lining. “This policy has taken us on a path to innovation,” said Bufalini. “A research programme under the umbrella of qualified state agencies has developed innovative uses of equipment never used before on such construction sites. The quality of the work carried out will hopefully become a reference in this field and prepare for improvements of the national standards.”

When operational, the 270km Lyon-Turin railway line will become the central ring of the European TEN-T Mediterranean Corridor, which runs from Hungary to southern Spain. As one of the nine axes of the TEN-T transport network, it will guarantee a solid connection between western and central-eastern Europe, aiming to boost the regional economy and to greatly reduce greenhouse gas emissions by moving freight traffic from the highways to the rail network.