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Geotechnical reconnaissance of an extensive cover-collapse sinkhole phenomena of 2020–2021 Petrinja earthquake sequence (Central Croatia)

2022; SAGE Publishing; Volume: 39; Issue: 1 Linguagem: Inglês

10.1177/87552930221115759

8755-2930

Ingrid Tomac, Biljana Kovačević Zelić, Dunja Perić, Dubravko Domitrović, Nataša Štambuk Cvitanović, Helena Vučenović, Jelena Parlov, Josip Stipčević, Darko Matešić, Bojan Matoš, Igor Vlahović,

Rock Mechanics and Modeling

This article presents geotechnical reconnaissance data that characterize the formation of 122 new and 49 historical cover-collapse sinkholes within 1.13 km 2 area in 12 months following the M W 6.4 earthquake that occurred on 29 December 2020, in Petrinja, Croatia. Data include a geological background, seismic sequence information, sinkhole geometric characteristics, rainfall data, and results of detailed geotechnical subsurface investigation. The sinkhole geometrical features were collected using aerial and satellite imagery, terrestrial lidar, and manual measurements. Soil properties and groundwater levels were obtained from four geotechnical boreholes, accompanied by in situ geotechnical characterization and standard penetration tests (SPTs). Soil parameters were obtained from consolidated undrained conventional triaxial compression, oedometer, soil water retention, and index tests performed on 31 soil samples. Clayey cover, 4–10 m thick, with sporadic gravel lenses overlying cavernous, intensely karstified carbonate rocks, characterizes the sinkhole area. Clays are mostly overconsolidated, with varying degrees of saturation ranging from very small to fully saturated. Seasonal and climate-induced variations in the groundwater table interact with artesian/subartesian karst aquifer, thus affecting the suction and the shear strength. Soil water retention curves (SWRCs) indicate that desaturation is possible for deeper groundwater tables, thus further affecting the effective stress, shear strength, and interparticle tensile forces. Finally, the observed vertical walls that accompanied sinkholes opening can occur in the overconsolidated cohesive cover clay layer with varying degree of saturation. The presented data provide essential geomechanical information necessary to understand the associated sinkhole failure mechanism. This article will help future investigators to perform detailed analyses and provide a background for complementing future sinkhole precursor research. Geotechnical, geological, seismic, and precipitation data generally indicate that the formation of cover-collapse sinkholes in the study area is a consequence of a specific local geological setting but is significantly expedited by earthquake-induced dynamic loading and complemented by multiple hydro-mechanical factors.