Assessment of Intact Rock Parameters and Their Conditional Upscaling to the Rock Mass Scale

Lithological, metasomatic, and structural heterogeneity in ore-hosting rocks limits the reliability of applying a single set of mechanical parameters without domain subdivision. This study evaluates intact rock properties, shear resistance along natural discontinuities, and conditional upscaling to the rock mass scale. The database comprised 232 laboratory records from 36 geotechnical borehole identifiers: 73 Brazilian tensile tests, 68 uniaxial compression tests, 49 triaxial compression tests, and 42 direct shear tests. Four domains were defined: D1, beresite-altered granodiorites; D2, diorites; D3, granodiorites; and D4, lamprophyre dikes. The lowest mean uniaxial compressive strength occurred in D1 (91.75 ± 40.65 MPa), whereas D2 showed the highest mean value, although its small sample size precludes confirmation as a domain characteristic. D3 provided the most representative dataset and exhibited intra-domain variability, while D4 showed the greatest variability in Young’s modulus (CV = 82.21%). Mean apparent cohesion along natural discontinuities was 0.125 ± 0.039 MPa for D1 and 0.140 ± 0.083 MPa for D3; D2 and D4 remain preliminary. GSI values of 48–58 were used only in scenario-based Hoek–Brown calculations. A ±5-point change in GSI altered equivalent rock mass strength by approximately −25% to −26% and +33% to +34%. The results support domain-based parameterization but require in situ verification.