30 terms · plain language · declared conventions
Rock mechanics glossary
Short definitions for terms used across the Rocklytics technical library. Definitions provide orientation; use the cited method source for engineering application.
- Anisotropy
- Direction-dependent material or rock-mass behaviour.
- Confining stress (σ₃)
- The lesser principal stress used in a triaxial strength description.
- Disturbance factor (D)
- Hoek–Brown parameter representing blast damage and stress relaxation, from 0 to 1.
- Effective stress
- Stress carried by the solid skeleton after accounting for pore pressure.
- Excavation Support Ratio (ESR)
- Q-system factor relating excavation purpose and acceptable risk to equivalent dimension.
- Geological Strength Index (GSI)
- Characterization of rock-mass structure and discontinuity surface condition used in Hoek–Brown parameter estimation.
- Hoek–Brown criterion
- Empirical nonlinear failure criterion for intact rock and rock masses.
- Intact UCS (σci)
- Uniaxial compressive strength of intact rock material.
- Joint alteration number (Ja)
- Q-system rating describing joint-wall alteration and filling.
- Joint roughness number (Jr)
- Q-system rating describing discontinuity surface roughness.
- Joint-set number (Jn)
- Q-system rating representing the number and configuration of joint sets.
- Kirsch solution
- Closed-form elastic stress solution around a circular opening in an infinite plate.
- Mohr–Coulomb criterion
- Linear shear-strength model commonly expressed using cohesion and friction angle.
- Plane strain
- Idealization in which strain normal to the analysis plane is taken as zero.
- Principal stress
- Normal stress acting on a plane with zero shear stress.
- Q-system
- NGI rock-mass classification built from six parameter ratings.
- Rock mass
- In-situ assemblage of intact rock blocks and discontinuities.
- Rock Mass Rating (RMR)
- Bieniawski classification based on six groups of geological and engineering observations.
- Rock Quality Designation (RQD)
- Core-based index describing the proportion of sound core pieces longer than 100 mm under its standard definition.
- Sensitivity analysis
- Systematic evaluation of how plausible input changes affect results.
- Sign convention
- Declared rule assigning positive and negative signs to stress or strain.
- Stress Reduction Factor (SRF)
- Q-system factor representing weakness zones, stress problems or squeezing/swelling conditions.
- Tangential stress (σθ)
- Normal stress acting around the circumference of an opening.
- Traceability
- Ability to connect an output to its input, source, method version and transformations.
- Validation
- Evidence that a model is adequate for its intended use; distinct from software verification.
- Verification
- Evidence that equations and algorithms are implemented and solved correctly.
- Water reduction factor (Jw)
- Q-system factor accounting for joint water pressure and inflow effects.
- Workflow provenance
- Recorded origin and history of data, assumptions and processing steps.
- Yielding
- Irreversible material response after an elastic or strength limit is reached.
- Equivalent dimension
- Q-system span, diameter or height divided by ESR for support-chart use.
Reference context
Terminology follows the linked method literature, including Practical Rock Engineering and the NGI Q-system handbook.