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.

RQD (%)

Rock Quality Designation as a percentage (0-100).

Jn

Joint set number Jn from the Q tables.

Jr

Joint roughness number Jr from the Q tables.

Ja

Joint alteration number Ja from the Q tables.

Jw

Joint water reduction factor Jw.

SRF

Stress reduction factor SRF.

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

Q

Q system rock mass quality value.

• Geological models are scale-, site-, method-, and calibration-dependent. Heterogeneity, anisotropy, sampling, diagenesis, pressure-temperature history, instrument response, boundary conditions, and empirical-correlation range can dominate the result.
• 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.

• Geological Strength Index GSI Calculator

  Estimate the Hoek Geological Strength Index from the 1976 Rock Mass Rating using the published relation GSI = RMR76 - 5 (valid for RMR76 > 23).

• Rock Quality Designation RQD Calculator

  Rock Quality Designation RQD = 100 * (sum of intact core pieces at least 10 cm long) / total drilled core run length.