Rock Shear Strength Parameter Evaluation
Fit and plot shear-strength envelopes for four rock and soil failure criteria.
Fits and plots rock and soil shear-strength envelopes for four failure criteria, in either principal-stress or shear-normal space, from parameters you enter or from laboratory test data.
What it does
- Generalized Hoek-Brown, Mohr-Coulomb, Barton-Bandis and power-curve envelopes, with the equivalent Mohr-Coulomb fit and rock-mass modulus for Hoek-Brown.
- Curve fitting to triaxial or direct-shear data by Levenberg-Marquardt, simplex or linear regression, with the sum of squared residuals reported.
- Import of RocData .roc, RocLab .rlb, CSV and tab-delimited files; export to clipboard, Excel with native charts, a PDF report, .roc, .rlb, PNG and SVG.
- Thirteen estimation aids behind the Pick buttons, each citing its source, converted into the analysis's own unit.
- Interactive stress and instantaneous Mohr-Coulomb samplers on both plots.
Before you rely on a number
- The estimation aids are transcribed from published literature and are marked provisional until a geotechnical reviewer has signed each one off. Check a picked value before it reaches a design.
- Envelope parameters are estimates. Site-specific testing supersedes any tabulated or fitted value.
- Deformation modulus is reported in MPa whatever the analysis unit is: Hoek-Diederichs is calibrated in MPa.
Physics core rockstrength 1.0.0. Every number on
this page is computed server-side by it.
Failure criteria
- Hoek, E., Carranza-Torres, C. & Corkum, B. (2002). Hoek-Brown failure criterion — 2002 edition. Proc. NARMS-TAC, Toronto.
- Hoek, E. & Diederichs, M.S. (2006). Empirical estimation of rock mass modulus. Int. J. Rock Mech. Min. Sci. 43, 203–215.
- Balmer, G. (1952). A general analytical solution for Mohr's envelope. Proc. ASTM 52, 1260–1271.
- Barton, N. & Choubey, V. (1977). The shear strength of rock joints in theory and practice. Rock Mechanics 10, 1–54.
- Bandis, S., Lumsden, A.C. & Barton, N. (1981). Experimental studies of scale effects on the shear behaviour of rock joints. Int. J. Rock Mech. Min. Sci. 18, 1–21.
- Mogi, K. (1966). Pressure dependence of rock strength and transition from brittle fracture to ductile flow. Bull. Earthq. Res. Inst. 44, 215–232.
- Hoek, E. (2007). Practical Rock Engineering. RocScience.
Estimation aids behind the Pick buttons
| Aid | Source |
|---|---|
| σci — intact uniaxial compressive strength Provisional | ISRM (1978) field estimates of strength; grades after Hoek & Brown (1997), Practical Rock Engineering Table 'Field estimates of uniaxial compressive strength'. |
| mi — intact rock constant Provisional | Hoek, E. & Brown, E.T. (1997). Practical estimates of rock mass strength. Int. J. Rock Mech. Min. Sci. 34(8), 1165-1186. Values as tabulated in Hoek, Practical Rock Engineering. |
| GSI — general rock masses Provisional | Hoek, E. & Marinos, P. (2000). Predicting tunnel squeezing problems in weak heterogeneous rock masses. Tunnels and Tunnelling International. System after Hoek (1994) and Hoek, Kaiser & Bawden (1995). |
| GSI — flysch and heterogeneous rock masses Provisional | Marinos, P. & Hoek, E. (2001). Estimating the geotechnical properties of heterogeneous rock masses such as flysch. Bulletin of Engineering Geology and the Environment 60, 85-92. Revised classification: Marinos, V. (2019). Bull. Eng. Geol. Environ. 78, 899-912. |
| D — disturbance factor Provisional | Hoek, E., Carranza-Torres, C. & Corkum, B. (2002). Hoek-Brown failure criterion — 2002 edition. Proc. NARMS-TAC, Toronto. Guidelines for estimating the disturbance factor D. |
| Ei — intact rock modulus Provisional | Typical ranges after Hoek & Diederichs (2006) and AASHTO (1989); prefer MR · σci where σci is measured. |
| MR — modulus ratio (Ei = MR · σci) Provisional | Hoek, E. & Diederichs, M.S. (2006). Empirical estimation of rock mass modulus. Int. J. Rock Mech. Min. Sci. 43, 203-215, after Deere (1968). |
| φb — basic friction angle Provisional | Barton, N. & Choubey, V. (1977). The shear strength of rock joints in theory and practice. Rock Mechanics 10, 1-54, Table 'basic friction angles for various rock types'. |
| JRC — joint roughness coefficient Provisional | Scale after Barton, N. & Choubey, V. (1977). Profiles are our own clean-room artwork, synthesised to the Z₂ each band implies via Tse, S.D. & Cruden, D.M. (1979), Int. J. Rock Mech. Min. Sci. 16, 303-307. They are calibrated to Barton's scale, not traced from his figures. |
| JCS — joint wall compressive strength Provisional | Barton, N. & Choubey, V. (1977); ISRM (1978) weathering grades. JCS equals σci for fresh joint walls and reduces with wall weathering. |
| c — cohesion Provisional | Indicative ranges compiled from Hoek (2007), Practical Rock Engineering, and standard geotechnical practice. Site-specific testing supersedes any tabulated value. |
| φ — friction angle Provisional | Indicative ranges compiled from Hoek (2007), Practical Rock Engineering, and standard geotechnical practice. Site-specific testing supersedes any tabulated value. |
| γ — unit weight Provisional | Typical saturated bulk unit weights from standard geotechnical references. The Hoek σ′3max formulae take γ in MN/m³ — note the conversion from the kN/m³ these are usually quoted in. |
Values marked provisional are transcribed from the cited source and have not yet been signed off by a geotechnical reviewer.
Failure envelopes
Principal stresses
Shear vs normal stress
Export
The Excel workbook carries every envelope point and native charts of the plots on screen. The PDF embeds the plots exactly as drawn — zoom, sampler marks and all.
Envelope data sampled from the computed envelope
References
Hoek, E., Carranza-Torres, C. & Corkum, B. (2002). Hoek-Brown failure
criterion — 2002 edition. Proc. NARMS-TAC, Toronto.
Hoek, E. & Diederichs, M.S. (2006). Empirical estimation of rock mass
modulus. Int. J. Rock Mech. Min. Sci. 43, 203–215.
Balmer, G. (1952). A general analytical solution for Mohr's envelope.
Proc. ASTM 52, 1260–1271.