Use this geological calculation for a transparent first-pass interpretation of measured rock, soil, fluid, well, stratigraphic, isotopic, geophysical, or seismic data under an explicitly selected model.

RMR76

Bieniawski 1976 rock mass rating (must exceed 23).

Estimate the Hoek Geological Strength Index from the 1976 Rock Mass Rating using the published relation GSI = RMR76 - 5 (valid for RMR76 > 23). The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

GSI

Geological Strength Index GSI.

• Geotechnical correlations and idealized failure models depend on stratigraphy, sampling disturbance, drainage, stress history, groundwater, density, anisotropy, scale, construction sequence, and laboratory or field method. Site-specific design requires investigation and code factors.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Compare independent measurements and models, retain units and analytical metadata, propagate uncertainty, and validate interpretations against logs, cores, maps, laboratory data, or field observations.

• Rock Mass Rating RMR Calculator

  Bieniawski RMR total from the five sub-ratings (strength max 15, RQD max 20, spacing max 20, groundwater max 15, joint condition max 30) with the standard RMR class boundaries.

• Hoek Brown Criterion Calculator

  Generalized Hoek-Brown peak strength sigma_1 = sigma_3 + sigma_ci*(m_b*sigma_3/sigma_ci + s)^a with m_b, s and a from GSI and the disturbance factor D (Hoek et al., 2002).

• Q System Rating Calculator

  NGI rock mass quality Q = (RQD/Jn) * (Jr/Ja) * (Jw/SRF) from the six Barton parameters supplied directly.