ABSTRACT
The use of TBM-EPB is a well-established method for constructing underground infrastructure in densely urbanized areas, providing a safe and efficient way to excavate large tunnels with minimal disruption to surface structures. However, dealing with shallow overburden and heterogeneous soils below the groundwater table poses significant engineering challenges, particularly when tunnelling under operational and sensitive surface infrastructure. In the case of the Florence high speed rail bypass, the first project to involve underground excavation beneath the monumental city of Florence, the presence of highly plastic clay soils and the associated risk of cutterhead clogging was the main source of risk during the underpass of the existing and operational high-speed railway line. To mitigate this risk, a successful combination of preventive techniques and corrective measures were implemented. These efforts ensured safer and more efficient operations, demonstrating the importance of tailored engineering solutions in complex tunnelling projects.
