GPR surveys for the prevention of karst risk in underground gypsum quarries: Fid-Bau Portal

GPR surveys for the prevention of karst risk in underground gypsum quarries

Caselle, Chiara / Bonetto, Sabrina / Comina, Cesare / Stocco, Stefano

Highlights • “GPR guide” for the identification of karst anomalies in gypsum. • Investigation of the space behind the excavation face in underground drifts. • Key features for the discrimination of the filling (ai‘r, water or clay). • The filling discrimination depends on the size of the anomaly (cave or conduit).

Abstract The investigation and prediction of geological anomalies in underground quarries is fundamental to ensure safety, efficiency and economic convenience of the exploitation. For these aims, non-destructive geophysical surveys may be an effective alternative approach to classical destructive prospecting techniques (i.e. horizontal drilling), with great advantages particularly in complex geological frameworks and in areas subjected to specific geo-hazards. Ground Penetrating Radar (GPR), for its high resolution, is a suitable technique for underground excavations, particularly for the identification of water bodies, fissures and fractured rocks. The present study is focused on the application of GPR for the prediction of karst structures in underground gypsum quarries. Karst phenomenon is a main risk factor for gypsum orebodies, where large cavities may be intersected by the excavation. The possible filling with clay or pressurized water of these cavities exponentially increases the dangerousness of the phenomenon, due to swelling problems and violent water inrushes. The aim of the present study is to propose, through modelling and field surveys, a description of GPR outputs for principal elements of karst hazard in gypsum bodies, with particular attention to the discrimination of fillings (air, water or clay).