Rock Cut-Slope Quarry Assessment (NW Portugal): A Preliminary Hazard Assessment

To safeguard the operations in rock quarrying, it is required to evaluate slope stability hazards systematically. This work investigates the slope stability in a rock quarry in NW Portugal and demonstrates the significance of geological, geotechnical, and geomechanical in situ investigations. The rock mass is a monzogranite, medium-grained, two-mica, essentially biotitic, predominantly fresh to slightly weathered (W_1-2) to moderately weathered (W₃), and highly fractured. The geomechanical classifications and geotechnical indexes RMR, GSI, SMR, SQR, and Q‐Slope allowed five geomechanical zones. Globally, the Southern part of the quarry has a fair to very good quality and the Northern part has a poor to fair quality. Three cut-slopes were studied in the Northern part of the quarry, which was considered unstable to partially stable. Several potential failures may occur, namely wedge slides and toppling failures. The application of the RHRSm2 system and the SQI permitted the classification of the cut-slopes with a high to very high-risk level and an urgent to very urgent intervention. RocFall and Swedge Rocscience software were used to model block fall in different areas and potential rock failures.