Artificial caves as a possible danger: sinkholes and other effects at the surface

Artificial caves may represent a possible danger, threatening the public and private properties. Presence of underground cavities beneath built-up areas implies situations of potential risk for all the man-made infrastructures and constructions above. Nevertheless, such a risk remains unknown until an effective knowledge about the real extension, the typology, and the stability conditions of the caves has been reached. Cavers must be well aware of such a risk, and be ready to provide a contribution in facing the problems that might occur. In many occasions, development of deformations at the surface, up to subsidence and eventually formation of sinkholes, has caused severe direct damage, and produced a number of related problems, from inconveniences to circulation for the local population, to decreased value of properties, and so on. The conditions possibly leading to occurrence of sinkholes must be therefore object of study by cavers, since they are the only “eyes” that have a direct possibility of inspection and monitoring of the underground. Artificial cavities, once abandoned, are subject to degradation of the rock mass, which may also be favored by water infiltration, presence of wastes, or other anthropogenic actions (i.e., overcharge, vibrations due to traffic, etc.). Identification of the first signs of instability underground, in the form of tension cracks, deformations along the wall of the cavities, and first detachment of volumes of rocks, is crucial to assess the instability conditions at the site, and to plan the necessary interventions. All the above issues will be dealt with in this contribution, by means of some examples from Apulia region (southern Italy) where in recent years several episodes have occurred, mostly related to underground quarries. This latter typology of artificial caves has been identified by far as the most dangerous typology of artificial cavity concerning instability phenomena and the likely effects to the human societ