What it calculates
The tool calculates Hoek-Brown parameters and stress envelopes from intact-rock strength and rock-mass classification inputs.
- Rock-mass constants mb, s and a
- σcm, σt and σ3 limits
- σ1-σ3 and τ-σn failure envelopes with Mohr circles
- Equivalent c′ and φ′ for a selected σ3 range
Inputs
Enter intact-rock strength, rock-mass quality, disturbance and parameters required by the selected modulus method.
- σci, GSI, mi and disturbance factor D
- MR, Erm, RMR or Q depending on the selected method
- γ and H for some tunnel/slope stress-limit methods
- Rock test measurements or laboratory data, if available
Outputs and reports
Results show rock-mass constants, strength limits and the equivalent strength pair for the selected range.
- mb, s, a, Ei/Erm and σcm/σt
- σ3max, σ3n, c′ and φ′
- Stress envelopes and Mohr circles
- Optional rock-foundation screening and model fitting to test data
Validation
The Hoek-Brown validation document scopes numerical consistency against canonical equations and independent code implementations.
- Sixty-three JavaScript comparisons across seven rock cases and nine quantities PASS, with a reported maximum relative error of 0.0.
- The independent Python implementation reports a maximum relative error of 4.67e-16.
- These checks are not a cross-validation against third-party design software or an approval of design safety.
Who it is for
The tool is intended for rock mechanics and geotechnical engineers assessing rock-mass strength.
- Engineers using GSI and intact-rock strength data
- Teams reporting a selected σ3 range and equivalent strength parameters
Frequently asked questions
What do GSI, mi and D change?
These inputs determine the rock-mass constants mb, s and a.
Why do equivalent c′ and φ′ vary by method?
The Mohr-Coulomb equivalent is fitted over the selected σ3 range; general, tunnel and slope methods can use different ranges.
Can the Bieniawski rock-mass modulus method be used for any RMR?
The guide says the method requires RMR > 50 and recommends Serafim-Pereira for lower RMR.
Has the result been checked against third-party software?
The source validation document says cross-validation with third-party rock mechanics software is not documented.