Table 2 Classification of coal body impact tendency.

From: A novel experimental study on impact tendency of real time borehole coal samples under lateral constrained compression

Category

I

II

III

Impact tendency

No

Weak

Strong

Uniaxial compressive strength/MPa

RC < 7

7 ≤ RC < 14

RC ≥ 14

Dynamic failure duration/ms

DT > 500

50 < DT ≤ 500

DT ≤ 50

Impact energy index

KE < 1.5

1.5 ≤ KE < 5

KE ≥ 5

Elastic energy index

WET < 2

2 ≤ WET < 5

WET ≥ 5

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