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The construction site of the Turin-Lyon high speed rail line (Tav), Val di Susa Torino 09 agosto 2019 ANSA/TINO ROMANO
The construction site of the Turin-Lyon high speed rail line (Tav), Val di Susa Torino 09 agosto 2019 ANSA/TINO ROMANO

Chiomonte construction site

Excavation of the 12.5 km base tunnel in Italy, from Chiomonte to Susa, and construction of the junction on the A32 motorway

In Chiomonte there is the largest Italian construction site for the Lyon-Turin railway line. Since 2012, it has been a site of strategic national interest and is the Italian access route to the base tunnel.

To guarantee the safety of workers and citizens, in 2018 the CIPE approved the variant design that provides for the start of the base tunnel excavation on the Italian side from the Chiomonte construction site – already operational for exploratory work – instead of from Susa as initially planned.

The site measures 12 hectares and is located in the municipalities of Chiomonte and Giaglione, under the viaduct of the A32 motorway.


Preparazione dello scavo del tunnel di base

Avanzamento a gennaio 2024

A Chiomonte il nuovo raggruppamento d’imprese procede con l’installazione del cantiere e le attività necessarie a preparare il sito per gli scavi: montaggio delle strutture di cantiere e installazione delle attrezzature e dei materiali, attuazione del progetto esecutivo per le lavorazioni previste e per ordinare le due frese che dovranno scavare fino all’imbocco di Susa.

Key data

2 dual mode TBMs

30 km of excavations

worker icon

700 workers at the peak of activity

one billion euro worth of work

Groups of companies at work

TELT awarded the one billion euro work contract to the UXT group of companies composed of Itinera (group head), Ghella and Spie Batignolles. The project management was awarded to the group of companies, composed of Italferr, Systra Italia and Pini Group SA.

Work techniques

A total of approximately 30 km of excavation work is planned with both conventional method and TBM. In addition to the two base tunnel tubes, further excavations are planned: the Maddalena 2 tunnel, from where the tunnel boring machines will start, the bypasses between the two tubes, the Clarea safety site and the artificial tunnel at the Susa eastern entrance. For the excavation from the Clarea safety site to Susa, the use of two dual-mode TBMs is planned; these are capable of changing their advancement mode according to the type of terrain they have to face.


Maddalena 1 excavation​

Between 2012 and 2017, the Maddalena exploratory tunnel was built to explore the mountain through which the new line will travel. The 7,020-m-long exploratory tunnel was excavated by the GEA TBM, an open TBM with a diameter of 6.30 meters. This work served to explore the Massif d’Ambin, up to the maximum overburden (over 2000 metres) of the Mont Cenis base tunnel. The work made it possible to collect all the geological, hydrogeological, geomechanical and excavation data necessary to refine the design knowledge framework of the base tunnel in view of the final works. The construction site met these objectives in compliance with the environmental, contractual and budget parameters foreseen. When fully operational, it will be used as a service, safety and ventilation tunnel for the new tunnel.

Tunnelier Gea - Chiomonte

Interchange niches inside the Maddalena 1 tunnel

Construction of the niches necessary for the logistics of construction vehicles inside the Maddalena 1 tunnel. The niches (each 3 m deep and 30 to 40 m long) are constructed every 300 – 400 m along 7 km. They will transform the tunnel, which was created for exploratory purposes, into an access point for the construction vehicles of the base tunnel.

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