The underground cavities in the territory of Rome: typologies, distribution and sinkhole susceptibility

The present work describes the state of the knowledge regarding the distribution and types of the underground cavities in Rome urban center. The disasters related to the frequent phenomena of roof collapse of these cavities allow to recognize more than 2,600 potholes since 1875. The presented work constitutes the results of the Working Group formed in the framework of the "Project sinkholes in urban centers" for the city of Rome. The project involves three working phases: 1) data collection (underground cavities, sewer network, subsidence events); 2) identification of possible areas of pits triggering; 3) definition of the areas with different susceptibility to collapse. The project is aimed to improve the knowledge of the real extension of underground cavities, of the sinkhole phenomenon and the related risk, and will provide the local government useful information for the definition of geological-technical requirements for the civil protection and urban planning activities. The real extension of underground cavities are unknown. The first cavities in Rome, realized for supply of building materials, were excavated before the first century and reused as catacombs from the 2nd century onwards.