Abstract Karst science is beginning to recognize and understand better the interaction between conduits and the fractures and/or pore spaces within the aquifer. The relationship has important significance in relation to the understanding of contaminant transport, resource management and dewatering practices. This study presents the results of a dye trace carried out to investigate the link between the aquifer and conduits near a large dewatered quarry in the Mendip Hills in Somerset, England. At the point of undertaking the study, there were no records of the quarry directly intercepting any conduits but water from the conduit(s) is known to be drawn into the quarry. During the study, water from the conduits was observed to be lost to and gained from the fractures in different places in the aquifer. This complexity highlights the dependence of conduit flow on water levels in the aquifer and the sensitivity of groundwater in karstified aquifers to contamination.

Abstract Sinkholes are the main hazard related to underground voids of both natural and anthropogenic origin. Instabilities developing underground may propagate upwards in a dramatic manner and reach the surface in the form of a sinkhole. The Apulia region in southern Italy is an interesting case study due to the outcropping of soluble rocks throughout the region. These rocks are affected by karst processes and have a high number of anthropogenic cavities. The latter were excavated by humans at different times for a variety of purposes. The worrying recent increase in the number of sinkhole events registered in Apulia led us to collect information on natural and anthropogenic sinkholes in Apulia. We focused on anthropogenic cavities, mostly excavated in Plio-Pleistocene calcarenites, and characterized the rock masses before using two- and three-dimensional parametric numerical analyses to model the instability processes, with the aim of exploring the failure mechanisms that lead to the occurrence of sinkholes. The parametric studies allowed us to carry out a preliminary evaluation of the stability conditions through simple charts designed for use in the field.