Analysis and Application on Controlling Thick Hard Roof Caving with Deep-Hole Position Presplitting Blasting

Table 7

PPV critical values.

Vibration velocity (cm/s)	Damage degree corresponding to different vibration speeds	Medium sandstone remark
<24	Rock mass without fracture	–
26–63.4	Low development of fractures in rock stratas	31–47 cm/s
63.5–254	The tensile crack is serious in rock stratas with radial cracks locally developing	48–170 cm/s
>255	Rock mass is completely broken	>171 cm/s