Search

The work deals with the design of two tunnels, currently under construction, connecting the existing Municipio Station access 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 have to underpass archaeological remnants consisting in fortification walls built in the sixteenth century, through a subsoil composed by a loose silty sand overlying a soft and sometimes fractured rock (Neapolitan Yellow Tuff) and below the groundwater table. The design and the choice of the 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.

A Metro Line 1 extension is being executed in Naples from the terminal of Dante Station. The new underground section is composed of five new stations and two twin rail tunnels with a length of 5 km. Toledo Station has the shaft located laterally and a large size service tunnel (13 m wide, 17 m high and 40 m long) connects it to the rail and pedestrian access tunnels, starting from the access shaft. The tunnel is located in the historical centre, under a deeply urbanized area in volcanic soil (loose pozzolana silty sand and tuff) with a hydrostatic head of 27 m. For stabilizing the tunnel crown in loose volcanic soil, it was decided to adopt the Artificial Ground Freezing method among the various options of ground improvement techniques. In this paper, the observed behaviour is presented and discussed, allowing to throw a light on the effects of the rather complex execution steps of the underground excavations

This paper is concerned with the analysis of a 13 m wide, 17 m high and 40 m long service tunnel execution at Toledo Station within the Metro Line 1 extension project in Naples (Italy). From the terminal of Dante Station, the new stretch of the underground is composed of five new stations and two twin rail tunnels with a length of 5 km. Four stations out of five have the access shaft centered with the twin rail tunnels. On the contrary, Toledo Station, situated in the deeply urbanized historical centre of the city, has the shaft located laterally and a large size service tunnel connects it to the rail and pedestrian access tunnels, starting from the access shaft. The subsoil concerned can be divided schematically into two main layers: a top loose silty sand overlying the soft and sometimes fractured Neapolitan Yellow Tuff, with a hydrostatic head of 27 m above the tunnel invert. In this work, a more refined and thorough back analysis of the full construction process of the service tunnel was implemented starting from the drift construction and passing through the freezing process of the soil with the pore water, the excavation with the soil removal and the final thawing step. To this purpose a 3D model was built into the general purpose DFM software package named Flac3D

The new stretch of Metro Line 1 in Naples (Italy) consists of five new stations and two twin rail tunnels with a total length of about 5 km. Toledo Station is situated in the deeply urbanized histori-cal centre of the city. The main shaft is located by a side of the line and it is connected to the pedestrian platforms by a large size service tunnel, 13 m wide, 17 m high and 40 m long. Figure 1 represents a longitudinal section of the main shaft of the station and of the service tunnel with the above and surrounding buildings.

The multi-award-winning Toledo station on Metro line 1 in the Spanish quarter of Naples, Italy, has been described as one of the most impressive and beautiful in the world. Designed by architect Oscar Tusquets Blanca and completed in 2012, the station also uniquely serves as an underground museum, blending iconic architecture, contemporary artworks and 500-year-old archaeological remains. In the 5 years since its opening the station has won many awards and helped Naples win the 2019 World Tunnelling Congress. This paper first describes the excavation of the station’s unusually large platform access tunnel in unstable water-bearing soft rock and loose sand, which required a complex combination of cement–chemical grouting, ground freezing and extensive monitoring. It then explains how archaeology, architecture and art were successfully integrated into the resulting underground spaces.

The paper is dedicated to the case history of a 13 m wide, 17 m high and 40 m long service tunnel at Toledo Station, previously constructed in a deep open shaft and belonging to the Line 1 of the Napoli underground network. The existing Line 1 has been recently extended with a new stretch consisting of five new stations connected by twin rail tunnels for a total length of about 5 km. Toledo Station main shaft is located by a side of the line and it is connected to the pedestrian platforms by the above mentioned large size service tunnel. The station is situated in the historical center of the city of Napoli, under a deeply urbanized area. In Fig. 1 a longitudinal section of the main shaft of the station and of the large service tunnel with the above and surrounding buildings is sketched. The focus of this paper is on the settlement caused by the tunnel excavation and on the use of the Artificial Ground Freezing (AGF) technique to allow the safe excavation of the large crown of the service tunnel, located about one half in a silty sand layer and one half in yellow tuff, well below the groundwater table.