| Hoek & Brown [42] | Grimstad & Barton [44] | Palmstorm [45] | |||
| Ratio (σc/σΘ) | Description | Ratio (σc/σΘ) | Description | Competency Factor (Cg) | Failure Modes |
| σc/σΘ > 7 | Stable | σc/σΘ > 100 | Low stress, near surface, open joints | <2.5 | No rock stress induced instability |
| σc/σΘ = 3.5 | Minor sidewall spalling | σc/σΘ = 3 - 100 | Medium stress, favorable stress conditions | 2.5 - 1 | High stress, slightly loosening |
| σc/σΘ = 2 | Severe spalling | σc/σΘ = 2 - 3 | High stress, usually favorable to stability, maybe unfavorable to wall stability | 1 - 0.5 | Light rock burst or spalling |
| σc/σΘ = 1.7 | Heavy support required | σc/σΘ = 1.5 - 2 | Moderate slabbing after one hour | ||
| σc/σΘ < 1.4 | Severe rock burst problem | σc/σΘ = 1 - 1.5 | Slabbing and rock burst after minutes in massive rocks | <0.5 | Heavy rock burst |
| σc/σΘ < 1 | Heavy rock burst and immediate rock deformation | ||||