The project ofhigh speed/high capacity Naples-Bariwhich will halve the train travel time to go from the Campania capital to the Apulian capital, is under construction.
The new line will allow trains to travel 145 km in two hours, with trains having a maximum speed of 250 km/h. The project, which speeds up the itinerary between the two cities, started between 2015 and 2016, and will cross various internal territories to connect communities and economies at risk of depopulation by reducing travel times. But there is also a benefit for the capital: if from Naples it will take 2 hours to reach Barifrom Rome it will take about 3 hours instead.
Geopop was lucky enough to go to the construction site and see how far the works are, to show everyone how complex is it to dig 650 meters of tunnel.
As reported by the State Railways website, the works of AV/AC Naples-Bari they should finish by 2028, although some routes will be active even earlier, allowing the duration of the journey to be reduced – even if partially.
How they are building the Naples-Cancello high-speed section
Building railways along a plain is not difficult, but if you have to cross the mountains, the tune changes: building a route crossing Italy from east to west is very complicated when – as in this case – you have to face the Apennines.
Beyond this, not everyone knows what happens during the works of a project of this kind, and it is precisely for this reason that we went to one of the construction sites of the route, Naples-Cancello, where they are digging a tunnel that passes under a pre-existing track.
First, the tunnel walls, the so-called diaphragms, transverse diaphragms and the ceiling were built. In practice we are talking about a concrete “box”, which is the casing of the tunnel that must be excavated and emptied.
This box, however, has everything but not a base, so if while digging you encountered a water table, water would emerge under your feet.
Well, underground, there are aquifers. This means that if you dig deep, at some point you will find water. But then how does the tunnel not flood instantly?
To avoid flooding, the base of the tunnels is usually waterproofed and cemented. In the case of the Naples-Bari section, the route was chosen to dig the tunnel hyperbaric techniquewhich had never been used before in Italy for this type of work.
This technique consists ofinject compressed air in the tunnel (which is sealed: you dig, but the duct behind it must be closed, otherwise the air comes out) to increase the air pressure and push the water down. The entire excavation proceeds in these hyperbaric conditions, with a pressure between 0.3 and approximately 1.2 atmospheres: this means that the people who work here are as if they were working with the pressure that exists between 3 and 12 meters below water, and it takes workers up to half an hour to get used to working with this type of pressure. No danger, however: the workers have followed both theoretical and physical training courses, and know how to intervene in the event of various problems. The work continues non-stop, 24 hours a day, 7 days a week with alternating shifts.
And all the excavated material… what happens to it? Where does it come from if the tunnel is sealed?
At the entrance there are two large rooms connected to the inside of the gallery, therefore also pressurized. An automated treadmill system brings the excavated materials inside them. When a room is full, the internal door (the one connected to the tunnel) closes and the external one opens, so the excavated materials can be taken away. In the meantime, the other room is used so as not to interrupt the flow.
But… how do the workers manage to breathe with all the exhaust fumes of the diggers? Don’t worry: electric excavators are used in the tunnels.
The HS/AC Naples-Bari line, which will improve travel times for hundreds of people, is an engineeringly complex but sustainable work, because protects the aquifer avoiding letting it come into contact with cement and other additives.
