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Criteria for determining impact propensity of coal.
| Form | Dynamic destruction time (ms) | Impact energy index | Uniaxial compressive strength (Mpa) | Propensity to shock |
|---|---|---|---|---|
| Category I | DT > 500 | KE < 1.5 | σc < 7 | None |
| Category II | 50 < DT ≤ 500 | 1.5 ≤ KE < 5 | 7 ≤ σc ≤ 14 | Weak |
| Category III | DT < 50 | KE ≥ 5 | σc ≥ 14 | Vigorous |
