Rock Mass Classification: Q_SYSTEM
Rock mass classification systems — RMR (Rock Mass Rating), Q-system (Barton), and GSI (Geological Strength Index) — with rating ranges, rock quality descriptions, support recommendations, and estimated strength/deformation parameters
| classification system | parameter or class | estimated modulus gpa max (GPa) | estimated modulus gpa min (GPa) | friction angle deg min (deg) | notes | rating max (dimensionless) | rating min (dimensionless) | rock mass description | rqd pct range |
|---|---|---|---|---|---|---|---|---|---|
| Q_SYSTEM | Exceptional | 80 | 30 | >55 | Q=RQD/Jn x Jr/Ja x Jw/SRF; Q=400-1000; exceptionally good quality hard rock; no support required | 1,000 | 400 | Exceptionally Good | 95-100 |
| Q_SYSTEM | Extremely_Poor | 0.5 | <0.1 | <25 | Q=0.001-0.01; squeezing or swelling rock; cast-in-place concrete lining; heavy support; yield elements | 0.01 | 0.001 | Exceptionally Poor | <10 |
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