Sinkholes induced by the Petrinja M6.2 earthquake and guidelines for their remediation

Abstract

This paper proposes a remediation solution for the sinkholes appeared as a consequence of a devastating earthquake of 6.2 magnitude which hit Croatia in December 2020. At the time of writing this paper, more than 90 sinkholes in villages Mečenčani and Borojevići opened, all triggered by the main impact as well by the series of aftershocks, leaving both authorities and public, as well the professional -scientific community, in surprise. The sinkholes are identified as the cover collapse sinkholes, a most dangerous type of a sinkhole which collapses without any prior ground surface deformation. Owing to the fact that the conditions for the formation of these phenomena are in geological setting of this sinkhole prone area, characterized by the proluvial deposits underlain by the soluble karstic rock mass, the necessity of appropriate investigation works and remediation techniques is highlighted. Since the sinkholes are presumably wellintegrated into the karstic conduit system of the aquifer, part of which is a water supply source Pasha's spring, the remediation techniques should rely on the permeable grained fills with minimized utilization of cement or chemical -based materials.