When it opens in 1999, the Naples and Rome link will be the first section of Italy's high speed rail network to be operational. The section includes 10km of works within the urban area of Rome forming the link to the city's edge and the station works at Rome's central Termini and other through stations.
Work started in 1995 on the 220km section through the Apennine mountains which reach almost to the West coast of Italy. Tunnelling accounts for 17% of the route and was carried out first, as it was considered to be the most complicated, technically demanding and time consuming aspect of the contract. Another reason was that tunnel spoil is used for engineering fill along other sections of the route.
The longest tunnel is a 6.6km long single bore through Colli Albani, 30km south of Rome. Contracting consortium Pegaso (Astaldi, Ansaldo and CCC) excavated two side adits 270m and 290m long to give six working faces (one at each end of the route and two at each adit). These start above the alignment and slope down to the tunnel, and will also form the emergency exits for the completed tunnel itself.
Excavation was relatively straightforward through the prevailing stable volcanic basalt. Although the material is strong, drill and blast was only used when drilling progress slowed to less than 7m per day. Using heavy excavators with hammer drills to excavate 1.5m and then steel ribs and shotcrete installed.
In situ casting of concrete lining segments was carried out using purpose- built 12m long steel shutters made by Libra, able to allow casting of three lengths of lining in a week.
Near Ferentino, 80km south of Rome, two tunnels have been built using similar techniques. These are 1.5km and 1.8km long and pass through more difficult ground, despite the predominant basalt. At the 2.5km long Macchia Piana tunnel, the basalt is interspersed with sand lenses and laced with underground streams. The tunnel was excavated in three sections, the upper running some 300m ahead of the middle section.