Method selection guide
RMR vs Q-system vs GSI
A practical comparison of three related but non-interchangeable systems: what each describes, what it needs and what it should not be asked to decide.
Core relationship
No universal conversion: preserve the original observations and each system’s edition, ratings and purpose.
Inputs & units
- Purpose of the assessment
- Available mapping and testing
- Excavation geometry and support question
- Required downstream model inputs
Assumptions
- Each system is applied from its own source definitions.
- Correlations are treated as local, conditional evidence—not identities.
- The geological domain and uncertainty are documented.
Limitations
- Similar-looking class labels can conceal different meanings.
- Published correlations commonly have dataset and range limits.
- Classification does not replace a geotechnical model, failure-mode assessment or observational feedback.
Synthetic worked example
Use RMR for its classification framework, Q for Q-system classification and empirical support context, and GSI within the Hoek–Brown parameter workflow. Compare their evidence, not just their final numbers.
Engineering use boundary
This page is educational and supports preliminary assessment. It does not replace site investigation, competent engineering judgement, final design, independent review or permitting requirements.