TERRATEC EPB TBM Selected for Palermo Underground Rail Project in Italy

TERRATEC is pleased to announce that one of its Earth Pressure Balance Machines (EPBMs) has been selected to drive the final section of Palermo's underground ring railway — the Politeama–Notarbartolo Lotto II contract, in the capital of Sicily, southern Italy.

Purpose-built for the project, the new Ø8.18m EPB TBM is equipped with 12 electric motors delivering a combined cutterhead power of 1,320kW to excavate 817m of tunnel through the historic heart of Palermo. From its launch shaft, the machine will follow Via Malaspina, pass beneath Piazza Virgilio and Via Brunetto Latini, then negotiate one of the tightest curves on any active metro project in Europe — a 180m-radius alignment into Via Paternostro — before reaching final breakthrough at the Politeama Theatre.

A defining feature of the project is the TBM's ability to safely and accurately negotiate extremely tight horizontal geometry. The Ø8.18m EPB machine has been specifically engineered to manage the 180m-radius curve — a demanding requirement for a tunnel of this diameter in a constrained urban setting. This capability is achieved through an optimised articulation system, compact shield geometry and a high-torque cutterhead drive, allowing stable excavation even under asymmetric loading conditions.

The machine's steering system provides precise control of thrust distribution across the shield and articulation joints, enabling smooth curve negotiation without overstressing the segmental lining or inducing excessive ground disturbance. At the same time, the EPB operating principle ensures consistent face support through the curve by maintaining homogeneous chamber pressure and controlled muck flow — a critical factor when advancing beneath the densely founded historic structures above.

To accommodate the elevated lateral forces associated with tight-radius steering, the TBM incorporates a reinforced main bearing and a robust shield skin design. The back-up and segment erection systems have been configured to handle lined tunnel construction through tight geometry, including the erection of tapered rings where required, ensuring accurate ring build and long-term lining integrity throughout the curve.

The drive presents considerable additional engineering challenges. Beyond the tight-radius curve, the machine must contend with a maximum ascending gradient of 1.45% and a maximum descending gradient of 2.93%, all while passing directly beneath one of Palermo's most densely built-up and heavily trafficked urban districts, located just a short distance from the city's port.

Ground conditions along the alignment are highly variable, comprising a mixed sequence of clay, silt, sand and sandy gravels — a profile ideally suited to TERRATEC's proven EPB technology, which offers precise face-pressure control and minimal surface settlement in sensitive urban environments.

Site preparation works are currently underway, with TBM launch scheduled for the second quarter of 2027.

Once complete, Lotto II will close the ring of Palermo's underground metro, linking Notarbartolo station with the port area and the historic centre at Politeama. The new line will provide a fast metropolitan connection between the city centre and the Passante Ferroviario — the strategic south-to-north rail link that crosses Palermo from Palermo Centrale station to Falcone-Borsellino (Punta Raisi) Airport, effectively functioning as a surface metro for the wider metropolitan area.

Gianguido Babini, Production Director of D'Agostino Costruzioni, stated: "The Palermo railway ring is among the most eagerly awaited public works in Sicily." The project is expected to bring significant benefits to the city, easing chronic urban traffic congestion, improving air quality, and connecting strategic civic, cultural and transport hubs across Palermo.