Burst Failure Characteristics and Energy Evolution Law of Coal with Prefabricated Cracks at Different Angles

Table 1

Determination of burst tendency [29, 30].

Burst tendency	No burst trend	Weak burst tendency	Strong burst tendency
Dynamic destruction time (ms)	>500	50∼500	≤50
Uniaxial compressive strength (MPa)	<7	7∼14	≥14
Bursting energy index	<1.5	1.5∼5	≥5
Burst energy velocity index (s^−1)	<3	3∼100	≥100