Analysis of sinkhole triggering mechanisms in the hinterland of Naples (southern Italy)

This paper deals with the analysis and verification of the most frequently occurring triggering mechanisms for sinkholes in urban areas over mine caves. The study analyzes the phenomena observed in the hinterland of Naples (Italy), where intense historical mining activity has left several shallow underground man-made caves and tunnels. Collapse generally occurs due to the presence of an underground void, with or without involving the failure of the cave roof. The triggering is mainly due to the increase in water content in the soil due to anthropogenic causes such as leakages from aqueducts and sewerage systems. In this study, the stability condition of underground man-made caves was assessed through a parametric analysis based on a database of the geometry of the caves. The mechanical parameters assumed in the analyses were obtained from several stratigraphic logs, in-situ tests and laboratory investigations. The findings permitted a case study to be identified for 2D numerical analysis. Two triggering mechanisms (scenarios) were investigated in order to back-analyze field observations. The results reproduce the width and depth of observed phenomena and suggest that sinkhole risk mitigation in urban areas can be obtained first and foremost with enhanced knowledge of cave and tunnel networks, and also with proper maintenance of buried pipelines.