Hyperbaric excavation technique for the Casalnuovo tunnel

Italferr, an engineering company of the FS Group's Infrastructure Hub, is engaged in the Works Supervision of the Casalnuovo Tunnel excavation, present on the route of the first section of the Naples-Bari HS/HC link.

A never-before-used technique is being applied to carry out the work: tunnel excavation in hyperbaric conditions. This innovative and sustainable technique makes it possible to excavate the cut&cover tunnel, which extends below the water table, through the introduction of compressed air as a contrasting method to allow the excavation and tunnel lining work in the absence of water.

In fact, the pressure created inside the construction site allows water to be kept out of the work areas, ensuring advantages from an environmental point of view as well because it prevents the water table to come into contact with cement mixtures and chemical additives.

All this entailed the preparation of complex, state-of-the-art set up of systems, developed with the involvement of specialized technicians as well as highly qualified international suppliers.

As regards safety, in view of the special working conditions, several innovations were introduced such as, for example, procedures and specific technical and sanitary protocols such as to ensure maximum safety and health of the workers during the work stages and a consistently high level of performance.

More specifically, entry into the hyperbaric atmosphere of properly trained workers is planned through gradual adaptation operations in a special airlock. The same procedure is carried out in the exit phase. Depending on the excavation phases, pressure fluctuates between 0.3 and about 1.2 atmospheres. Outside the tunnel, on the other hand, there is always a sanitary garrison that, in addition to cooperating with the hyperbaric technicians in managing the in and out flow of workers from the hyperbaric atmosphere, can be activated at any time to perform all the necessary operations for the recovery of any injured persons.

The health protocol, prepared and managed by top national experts in the hyperbaric medical field, also includes monitoring the health conditions of workers on a bimonthly basis.

The equipment used inside the tunnel, on the other hand, is all strictly electric so as to avoid dangerous trigger effects and to guarantee the health of workers at all times.

Excavation of the Casalnuovo tunnel - which is about 650 meters long, crosses a heavily urbanized area and is scheduled to be completed by early 2025 - is taking place nonstop, 7 days a week, 24 hours a day, thanks to this new technique, which is one of the few applications of this procedure even at European level.