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Rock mass classification (or rock mass rating) is a quantitative empirical procedure by which the quality, competence, and expected engineering behavior of a jointed rock mass are summarized into a finite set of classes or an index number based on a small number of geomechanical parameters ^[1]. Typical input parameters include the uniaxial compressive strength of the intact rock, rock quality designation (RQD), joint spacing, joint condition (roughness, weathering, infilling), groundwater condition, and joint orientation relative to the excavation ^[2]. The two most widely used systems are the Rock Mass Rating (RMR) system of Bieniawski, which sums weighted ratings to classify the mass into five classes and to derive support recommendations, and the Q-system of Barton, Lien, and Lunde, which expresses rock-mass quality as a product of ratios of RQD, joint-set number, joint roughness, joint alteration, joint water reduction, and stress reduction factors ^[2][3]. Classification systems are distinguished from continuous rock-mass strength criteria (such as the Hoek–Brown failure criterion) by their empirical, table-based, and design-rule-oriented character.