How is rock mass behavior assessed for underground excavations?

Rock mass characterization uses classification systems: RMR (Rock Mass Rating) combining strength, RQD, joint spacing/condition, and water; Q-system with additional stress and excavation factors; GSI (Geological Strength Index). These correlate to support requirements and rock mass properties. Analysis methods: empirical (support charts), analytical (convergence-confinement), numerical (FE/FD with Hoek-Brown or Mohr-Coulomb). Design considers in-situ stress state, excavation sequence, support timing, and groundwater control. Monitoring with convergence pins and multi-point extensometers validates design.