Table 13 Excavation classes and limit values for underground excavations.
From: Re-evaluation of excavation class limits for underground excavations based on new data
Excavation class | Parameters and limit values | |||
|---|---|---|---|---|
σcm (MPa) | Basic RMR89 and Q | GSI | ||
Is(50) ≥ 3 MPa | Is(50) < 3 MPa | |||
Blasting | σcm ≥ 3 | Basic RMR89 > 55 and Q > 1 | GSI > 55 | GSI > 65 |
Hammer&Blasting | 1<σcm < 3 | 40 < Basic RMR89 < 55 and Q > 1 | 45 < GSI < 55 | 65 < GSI < 40 |
Hammer | 0.15<σcm < 1 | Basic RMR89 < 40 and 1 > Q > 0.2 | 30 < GSI < 45 | 40 < GSI < 30 |
Digging | σcm ≤ 0.15 | Basic RMR89 < 40 and 0.2 < Q | GSI < 30 | GSI < 30 |
