The high-speed underground rail link in the city of Florence is part of the high-speed railway between Milan and Naples, in Italy. Two single-track tunnels of about 6.5 km each link the southern end (Campo di Marte) and the northern end (Rifredi).
A cover between 5 and 27 m separates the tunnels from the existing urban structures. The excavation was performed with an EPB tunnel-boring machine to balance the stresses of the excavated ground. The machine diameter was 9.4 m. The excavation work below the densely constructed and populated city of Florence was subject to a high risk of subsidence.
The underground works were designed to ensure the serviceability of the existing infrastructures and buildings. Subsidence models were developed to estimate the effects of excavation on buildings, railway lines and city monuments. Innovative consolidation technologies such as “compensation grouting” were designed to contrast the subsidence risk.
SWS also provided a safety monitoring service for infrastructures affected by excavation during construction work.