Examples of anthropogenic sinkholes in Sicily and comparison with similar phenomena in southern Italy

Anthropogenic sinkholes affect several built-up areas of Sicily (southern Italy) representing a great risk to people, buildings, and infrastructures. These phenomena are generally associated with the presence of ancient underground quarries for the extraction of calcarenite rock, used for building or ornamental materials. These quarries were poorly constructed and abandoned throughout history. Field surveys, structural analysis of the fissure networks in the rock mass, and numerical modeling were carried out in order to understand the most significant factors responsible of the instability processes of underground quarries. The genetic mechanisms of anthropogenic sinkholes have also been investigated. Jointing and saturation conditions of the calcarenite, along with indiscriminate enlargement of voids, can reduce the available strength. This strength is needed to maintain the stability of the rock mass above the underground quarry, the lack of which can cause the sinkholes formation. Finally, a comparison between the cases of Sicily and Apulia regions, where similar anthropogenic sinkholes are widespread, was carried