S. No. | Rock classification | Strength (MPa) |
1 | Very weak | <1.25 |
2 | Weak | 1.25 - 5.00 |
3 | Moderately weak | 5.00 - 12.50 |
4 | Moderately strong | 12.50 - 50 |
5 | Strong | 50 - 100 |