New Colosseum Station of Rome underground line C
Geotechnical detailed design of underground structures

Client: Metro C Scpa
2007-2008

The new Colosseo Station will provide the correspondence between the existing B Line and the new C Line of Rome Underground. To this aim, two large and deep shafts will be constructed just beside the existing Colosseo station of the B Line; a system of pedestrian tunnels will connect this station with the Fori Imperiali station of the new and deeper C Line of the Underground.

Soil profile is constituted, from top to bottom, by ancients granular fills (up to 8 meters), pyroclastic sandy soils, sands and gravel and, finally, by overconsolidated stiff clays. Groundwater elevation is about 15 m a.s.l.: the bottom of the excavation is expected more than 20 m below groundwater level.

The main design issues regarded the study of appropriate technical solutions for managing the interaction effects between new and existing structures. In fact. due to the requested excavation depth (more than 30 m) of the shafts, significant effects are expected on the existing B Line structure (both on tracks and on station), and on existing buildings. In order to minimize these adverse effects, multi-propped retaining structures with cross-walls were selected.

The analysis of the behaviour of the excavation was studied with finite element methods (PLAXIS code) and, also, with codes based on elasto-plastic subgrade reaction method.