Settlement prediction of an historic masonry due to tunnel excavation taking into account soil-structure interaction

As a consequence of tunnelling in urban areas, the study of soil-structure interaction is receiving a growing interest, focusing on the assessment of the risk of damage induced in existing structures by excavation. The conventional approach used to evaluate the settlements derives from empirical rules, based on free-field conditions, and the damage level is assessed by representing the building as a simple beam whose foundations follows the movements caused by the tunnel excavation [1,2]. In the present paper, a numerical approach taking into account the soil-structure interaction is developed and implemented in the Finite Element code Abaqus. The structure, representing an ancient masonry, is schematised as a 2D homogenized anisotropic medium, whose yield criterion is derived via homogenization, starting form the mechanical and geometrical characteristics of brick and mortar [3]. The tunnel excavation is simulated by means of imposed displacement at the tunnel surface, while the soil is modelled through an elastic-perfectly plastic Mohr-Coulomb model. The numerical analyses are performed assuming plane-strain and plane-stress conditions for the soil and the masonry structure, respectively [4]. As a case study, the undercrossing of the ancient Aqueduct Felice in Rome by two shallow tunnels recently built for the new Metro C line is considered and the results obtained by the numerical analyses are compared to the monitoring data acquired during excavation.