Genoa Metro: Principe - San Giorgio Caricamento - Le Grazie Section, Italy

Genoa's metro is a key infrastructure of urban public transport, built in more than one phase with advanced technologies. In the first phase, the stations were built the Principe, Darsena and Caricamento underground stations, which vary in depth from 14 m to 17.50 m. In the second phase, the Sarzano and De Ferrari underground stations, through the widening and improvement of existing tunnels. The 1st functional lot of the De Ferrari - Brignole functional section is part of the third work phase.

The first phase included building line works and building the access shaft of Principe, Darsena and San Giorgio Caricamento. Due to high-pressure water during excavations, a EPB TMB (earth counter-pressure) was used for the first time in Italy, with a 6.30 metre and cutting head with tools for mixed loose/compact soil.  By using this type of TBM model, which was lowered down in the Principe shaft, it was possible to excavate two single-track parallel tunnels, for an overall length of 1,800 m to reach the Le Grazie shaft. The latter allowed, once the excavation of the tunnel on the sea's side was completed, rotating the TBM by 180 degrees, to then excavate the tunnel on the mountain side, so as to reach the shaft of the Principe station, from where the whole machinery was then subsequently removed.

During the first phase of the works, soil consolidation operations were also done to increase the building's stability and that of the close-by ring road. 

The second work phase concerned Sarzano and De Ferrari stations and improving 500 m of the existing line. The third phase of the project included works related to the train inversion system on the Bisagno river, the new Brignole station, and the new railway syste, that includes service shafts between the De Ferrari and Brignole stations, for an overall length of 1,250 m.