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

Table 3

Design of factor 3 level test.

Experimental scheme	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
4	2	120	10
5	4	150	6
6	6	90	8
7	2	150	8
8	4	90	10
9	6	120	6