ABSTRACT
The city of Florence is considered the icon of an extraordinary historical period for both Europe and Italy, the Renaissance. It is the cradle of cultural and artistic development, which started in Italy and then spread worldwide, profoundly marking the history of humanity.
The historical center of Florence, UNESCO Heritage Site since 1982, includes numerous remarkable works of art which make the city a big piece of art itself.
Today, Florence must adapt to the presence of both Florentines and tourists who reach, every year in December, the maximum number of 13 million people, against a resident population of 370.000 units.
Florence must therefore equip itself with modern and efficient infrastructures with a reduced impact on the environment, which can satisfy a constantly growing demand for both urban/regional and national mobility. This is particularly true if we consider that the configuration of the new Florence High-Speed railway hub falls within the Scandinavian Mediterranean Corridor of the TEN-T Networks.
The new railway underpass and the new High-Speed railway Station of Firenze Belfiore will free the surface network from the transit of high-speed trains and enrich the offer of services for the benefit of citizens and companies, as well as economic and tourist activities.
The urban section of the new high-speed/high-capacity railway line will develop for over 7km underground, with two single-track tunnels between the current stations of Firenze Rifredi and Firenze Campo di Marte. The project foresees the construction of the Belfiore high-speed station along the underground section in the Belfiore-Macelli area. In developing the executive project, we paid great attention to the pre-existing structures and buildings, which are included in the subsidence basin induced by the excavation of the two single-track tunnels. The construction of the tunnels will be carried out by an EPB TBM with a diameter of 9.4 m.
The analysis of the impact on pre-existing structures involved about 230 constructions. Among those buildings, our analysis, designing and modelling mainly involved famous historical sites such as Fortezza da Basso (1535), Opificio delle Pietre Dure (1340) and Piazza della Libertà.
To avoid any structural failure due to the subsidence process induced by the passage of the EPB TBM below Rastriglia and Canaviglia ramparts of the Fortezza da Basso fortress, we planned pre-consolidation interventions through the compensation grouting technique. It is based on interventions to be carried out before or, where necessary, during the excavation of the tunnels. This approach allows containing the predictions of damage on the structures within the zero class of Boscardin and Cording (1989).
A similar intervention has been carried out on the adjacent historical building "Opificio delle Pietre Dure", the former Monastery of San Niccolò di Cafaggio, dating back to 1340.
Instead, as far as the buildings facing Piazza della Libertà are concerned, our in-depth studies suggested not to carry out pre-consolidation interventions before construction but to pay particular attention to the monitoring of the excavated material, in terms of weight and volume. Furthermore, it is also essential to implement a subsidence monitoring system during construction to constantly keep the situation under control and avoid any possible damage.
