Probabilistic performance-based approaches to the static and seismic assessment of rock cavities

This paper demonstrates the applicability of a probabilistic performance-based approach to assess the stability of rock cavities under gravity and seismic loads, with reference to the case study of a Neapolitan room and pillar cave, located inside a rocky hill. An advanced 3D model was generated, importing in the numerical code the data acquired during a laser scanning-based geometrical survey. The careful reproduction of the on-site geometry was found to improve the reliability of the results of static and dynamic analyses; because (i) the load eccentricity induced by the irregular shape of the hill reduces the stability of pillars, (ii) the localization of the roof crack depends on the shape of the ceiling, and, furthermore, (iii) the global dynamic behaviour of the hill is affected by topographic effects. The safety factors of rooms and pillars computed after the seismic analyses were compared to their values before earthquake to highlight earthquake-induced modifications of the static equilibrium under gravity loads. Some considerations on the resilience of the cavity are reported based on the latter comparison.