Table 2 Qualitative and quantitative categorization of rock hardness.
Hardness | Qualitative characteristics | Rc (MPa) |
|---|---|---|
Hard | The hammering sound is crisp with rebound, shaking hands, harder to break; after soaking in water, usually there is no water absorption reaction | (60, 250] |
Slightly hard | The hammering sound is slightly crisp with slightly rebound, slightly shaking hands, hard to break; after soaking in water, slight water absorption reaction | (30, 60] |
Slightly soft | The hammering sound is not clear and crisp, no rebound, easy to break; after soaking in water, nails can be imprinted | (15, 30] |
Soft | The hammering sound is dumb, no rebound, dents, easier to break; after soaking in water, the hand can be broken | (5, 15] |
Extremely soft | The hammering sound is dumb, no rebound, deep dents, and the hands can be crushed; after soaking in water, it can be crushed into a ball | (0, 5] |
