The Chiaia Station of the Napoli Underground: Observations

Abstract

The focus of this paper is on the construction process of Chiaia Station belonging to the final stretch of Line 6 of Napoli’s underground network. The station is located in the old town district of Chiaia, surrounded by historical buildings and not far from the sea. The main box of the station is constructed within a 32.2 m × 39.5 m rectangular in plan excavation that reaches the maximum depth of 48 m below ground surface. The main shaft is supported in the upper portion by contiguous bored pile walls crossing the top pyroclastic sand layer and embedded in the Neapolitan Yellow Tuff (NYT) formation. The overall geometry of the excavation and many details of the site are such that a complex 3D modelling option is indeed required. A wide range of instruments has been used to supervise the safety of surrounding buildings and to measure ground and groundwater movements: optical survey points, consisting in marks on sidewalks, standard open pipe and Casagrande piezometers, inclinometers and extenso-inclinometers, installed in both NYT layer and bored piles. During excavation several anthropic cavities have been found in the NYT layer, making the excavation process slightly more complicated and risky. In the paper the construction process and the monitoring data are first presented. At the end collected data are compared with some empirical methods.