This construction method allows the excavation of the tunnel and the cladding phases almost simultaneously, thanks to the use of a TBM – Tunnel Boring Machine. The TBM allows a forward speed that is much higher than that of a “traditional” system, whatever the conditions of the terrain through which the tunnel passes.

Modern TBMs adapt to the terrain without requiring preventive consolidation of the excavated tunnel, except in exceptional cases. This is because excavation and paving of the cladding, with the placement of reinforced concrete ashlars, takes place at the same time, without any delay of the two phases, carried out with the help of sophisticated automation and control systems. At each advancement of the TBM, the tunnel behind it has already been completed. At that point, it is only necessary to provide the finishing: filling, ducts, road, systems.

Although TBMs require a considerable investment, they ensure reduced execution times, lower construction costs and increased worker safety, as well as precise costs and delivery dates.

For more than a decade, Toto has been working in the mechanized excavation sector, investing considerable resources to acquire the most performing TBMs. Among the main projects carried out there are the Martignano Tunnel (Trento) and the Sparvo Tunnel (lots 6 and 7 of the Variante di Valico) where Toto operated using the two largest milling cutters in the world.

Sparvo Tunnel

Lots 6-7 of the Variante di Valico

As tall as a 5-storey building, ,“Martina” is the world’s largest tunnel milling machine used by Toto Costruzioni Generali to dig the “Sparvo” tunnel, the most demanding of the Variante di Valico, consisting of two carriageways for a total length of about 5 km (2,431m for the northbound barrel; 2,495m for the southbound barrel).

Martignano Tunnel

S.S. 47 Valsugana (TN)

A double barrel tunnel was built under the village of Martignano (TN), each barrel 2,750 m long, excavated with a mechanised system and cladding with prefabricated reinforced concrete elements, 40 cm thick and 1,50 m long.