HyperbaricTunneling NaplesBariRailway TunnelConstruction

Italy’s First Hyperbaric Rail Tunnel Completed Under Naples: A Milestone in Geotechnical Innovation

*A 650-meter section of the 3.3-kilometer Casalnuovo Tunnel was successfully excavated using the hyperbaric tunneling method.*

The completion of the 3.3-kilometer Casalnuovo Tunnel along the Naples–Cancello high-speed railway marks a milestone in Italian geotechnical engineering. Approximately 650 meters of the tunnel were excavated using hyperbaric tunnelling, an advanced technique employing pressurized air to exclude groundwater and allow dry excavation. This was the first use of hyperbaric excavation in Italy.

The method avoided groundwater infiltration and eliminated the need for chemical additives, providing both engineering and environmental benefits. All excavation equipment was electrically powered, contributing to a zero-emission construction process.

Workers accessed the tunnel through a compensation chamber to gradually acclimate to the pressurized hyperbaric environment. Source: Tunnels and Tunnelling (image by Webuild)

The tunnel was hermetically sealed and segmented into watertight compartments. Workers entered via pressurization chambers, gradually acclimating to the hyperbaric environment. Specific health protocols and real-time monitoring systems ensured safety during 24/7 operations across the densely populated region.

Hyperbaric conditions demanded rigorous logistical coordination and precise execution, especially given the complex subsoil composition beneath Naples. The successful outcome not only highlights the viability of hyperbaric methods in urban tunneling but also sets a precedent for future Italian infrastructure projects.

The Casalnuovo Tunnel is part of the broader Naples–Bari high-speed line, which will span 145 kilometers, incorporating 15 tunnels and 25 viaducts. The entire route forms a key segment of the TEN-T Scandinavian–Mediterranean Corridor, enhancing mobility across Italy and into Europe.

Track installation on the Naples–Cancello section began in February 2025, with over 10 km laid so far. Once operational by early 2026, the tunnel will help cut travel times between Naples and Bari from four hours to two hours and forty minutes, with no need to change trains.

Sources: tunnelsandtunnelling.com, tunnellingjournal.com, railway.supply, tunnelingonline.com