ABSTRACT
The extension of Line 1 of the Naples underground passes through 5 stations. Each station consists of a rectangular central shaft, 4 platform tunnels with a length of approximately 50 m each and 4 escalator galleries connecting the platform level with the first slab above the rails (Colombo et al. 2008). As the tunnel alignment is at a distance of only 230 m from the coastline, the water table is close to the surface, leading to significant piezometric heads. The method of artificial ground freezing in a horizontal direction was employed as the most suitable method for ensuring stability and waterproofing of the platform and escalator tunnels. Figure 1 shows part of the Pari-Duomo platform tunnel in the Universita station. Its construction was completed prior to the excavation of the tunnel for the underground line using an EPB shield between the Universita station and the Duomo station.
