Abstract
The Hoek-Brown criterion is extensively employed in stability evaluations during underground mining, with m and s being the constants for friction and cohesion, respectively. Prior research has indicated that in massive rocks, damage initiation is primarily dependent upon loss of cohesion, which makes the s constant more significant. Although prior research indicated that s may differ from one rock mass type to another, it has been determined based on standard uniaxial compression tests. However, for inclined pillar design in dipping orebodies, the loading condition differs from standard uniaxial compression, and therefore the damage initiation stress cannot be determined from the standard uniaxial compression tests. To address this, this study applies the combined compression and shear test (C-CAST), developed for inclined pillar stability assessment, to determine more appropriate s values for different rock types. The resulting rock type-s values provide a more suitable basis for the design of inclined pillars under combined compression and shear loading conditions.