Building metro tunnels under downtown Naples, that has been declared as World Culture Heritage by the UNESCO, asks for especially responsible planning and the employment of efficient technology. Therefore, the tunnel route for the extension of the Line 1 from the Dante Station to the Garibaldi Station was planned at a depth of 20 to 40 meters deep below the buildings in the tuff strata.
In spring and autum 2004, two Herrenknecht EPB Shields got down to work for the excavation and the lining of the two parallel metro tunnels. In December 2007 and one year later in December 2008 the drives were completed successfully.
While the EPB Shields worked underground unseen, a Vertical Shaft Sinking Machine (VSM) by Herrenknecht was in operation well visible above ground. It excavated shafts from the surface down to the level of the tunnels that were to be used for ventilation or, if required, as excape shafts.
The VSM excavated ten shafts with diameters of 4.5 meters and depths of up to 45 meters proving best the machine technology's and working principle's efficiency. The VSM took up only very little space for its installation in the narrow streets of Naples and the noise exposure for the residents was very little. Because the excavation of the shafts and their lining with precast concrete elements could be realized simultaneously, the production of the shafts could be finished quickly with performance rates of up to five meters per day. After completing one shaft, the VSM could be rapidly disassembled and transported to the next jobsite due to its modular setup.