Trenchless trends help central Naples build metro station

摘要

AS PART of a continuing work programme to create an underground metro system in Naples, Italy, contractor Pizzarotti is undertaking a drilling operation to help develop the metro station at Piazza Garibaldi, opposite the mainline railway station in the city centre. The project highlights the growing interdependence of traditional tunnelling technology and methods more commonly seen as 'trenchless' in nature. Work, which began in January 2002, is due for completion in March 2007. Initially, the external underground walls for the station were excavated and filled with reinforced concrete. Once this was completed, excavation of the internal area could begin. Large supporting beams were required as the excavation grew deeper. Once at the required depth, the station excavations will be intersected by the train running tunnels, currently being constructed using a tunnel-boring machine. The space necessary for the passenger platforms at the stations will be extended beyond the station walls and underneath the piazza. Since two train lines will pass through the station, four 'galleries two on each side of the station, are needed. It was decided to use ground-freezing techniques to excavate these much wider' tunnels', so this required a pattern of boreholes to apply the ground-freezing fluids.