ABSTRACT
The paper deals with the design of twin tunnels, which construction has been completed on 2017, connecting the existing Municipio Station Line 6 main shaft (interchange node between Metro Line 6 and Metro Line 1 extension project in Naples, Italy) to the TBM extraction shaft located nearly 40 m far from it. The two short tunnels underpass archaeological findings consisting in fortification walls built in the sixteenth century, through a subsoil composed by loose silty sand overlying a soft and sometimes fractured rock (Neapolitan Yellow Tuff) and below the groundwater table. The design and construction processes have been very complex, adopting a mix of different measures as cement and chemical grouting at the sides and inverts in tuff and Artificial Ground Freezing at the crowns in sand, together with the compensation grouting technique, even for the obvious needs to preserve a unique archaeological site, part of mankind’s common heritage.
