Evaluating the effects of tunnelling on historical buildings: the example of a new subway in Rome. Auswertung der Auswirkungen des Tunnelbaus auf historische Gebäude am Beispiel einer neuen U-Bahnlinie in Rom

The construction of contracts T2 and T3 of the new Line C of the Rome Underground is to be carried out under the historical centre of the city, in an area of great archaeological, historical and artistic value. Significant problems derive from the geotechnical characteristics of the soil, from the presence of buried archaeological remains, and more significantly from the necessity of minimising the effects at the surface on the historical and monumental heritage. This paper illustrates the procedures adopted to evaluate the effects of tunnelling on the existing monuments and historical buildings, with particular reference to contract T2. Specifically, the study of the interaction between construction activities and the built environment was carried out following procedures at two increasing levels of complexity: Level 1 - green-field analyses were carried out first, neglecting the stiffness of the existing buildings for a simplified evaluation of potential damage induced by tunnel excavation; Level 2 - FE computations were then carried out in both two- and three dimensional conditions, accounting for the stiffness of existing buildings and considering possible long-term effects induced by drainage through the tunnel lining where necessary. The paper illustrates the main aspects of the procedure, using the example case study of Palazzo Grazioli.