Research on Optimal Design of Pressure Relief Blasting Parameters of Middle Rock Pillar in Near Vertical Coal Seam

Table 2

Factor level of the orthogonal test.

Level	Factor
	A	B	C
	Charge quantity (kg)	Blast hole diameter (mm)	Blast hole spacing (m)
1	2	90	6
2	4	120	8
3	6	150	10