The multifunctional shaft 3.3 is situated between the stations Amba Aradam-Ipponio and San Giovanni, near the garden next to the Via Sannio market on the Piazzale Appio side. This is the shaft from which the TBMs started the excavations of the tunnels towards Fori Imperiali.
The overall planimetric dimensions are 64.40 metres by 25.65 metres.
The Iron Floor varies between 8.940 metres and 9.120 metres above sea level inside the shaft.
The structure consists of 3 horizontal levels:
- A technical floor at a height of 25.47 metres above sea level (finished)
- An intermediate floor at a height of 16.54 metres above sea level (finished). This floor has the sole structural function of bracing the containment structures of the shaft
- A platform floor, at variable heights depending on the Iron Floor between 10.007 metres above sea level on the Amba Aradam side and 10.127 metres above sea level on the San Giovanni side.
The excavation technique is of the “top-down” type, which is the construction of downward structures. This minimalises the impact of the building site on the external surroundings.
Based on recommendations from the Archaeological Superintendence, the construction of the excavations up to the levels involved in Archaeological surveys (18.52 metres above sea level) have been carried out in an archaeological way that provides for subsequent horizontal layers.
The floors inside the “archaeological layer” were built only after having ensured an adequate height between the excavation floor and the soffit ceiling, necessary for the transit of excavation and material handling equipment. The use of prefabricated constructions has enabled us to avoid shoring up horizontal supports during construction whereby ensuring faster completion.
On the San Giovanni side are two large round holes with internal dimensions of 14.0 metres by 8.0 metres, for the insertion of the TBMs for the excavation of the line tunnels.