Sinkhole hazard quantitative assessment: Insights from the application of numerical modelling techniques

Sinkholes generated by the failure of underground caves represent a major threat to structures and infrastructures. Therefore, methods aimed at increasing the capacity to assess failure susceptibility, or even failure prediction, are needed. Phenomenological or heuristical methods, based on geomorphological or geo-structural evidences, have been largely used in the last decades. However, physically- or mechanically-based approaches allow to derive quantitative assessment of the equilibrium conditions of the rock mass and, as such, they allow to calculate proper safety margins against failure. Recently, the available numerical modelling approaches have shown to represent reliable methods to explore the evolution of stress-strain state of the rock mass and to understand the possible failure mechanism, without the need to advance a-priori assumptions on the failure mechanism. The contribution here proposed is aimed at presenting some insights into the recent advancements regarding the application of numerical modelling techniques to investigate the stress-state conditions leading to failure of underground caves or the safety margins with respect to failure. Further, the paper is aimed at discussing the techniques available to perform quantitative hazard assessment of underground caves, highlighting advantages and limitations of the different techniques, whose knowledge is necessary for a correct application of the methodologies. The proposed work shows some examples of the application of the numerical methodologies with respect to Southern Italy case studies, where artificial caves excavated in soft rock are particularly frequent.