Numerical Optimization of Drilling Parameters for Gas Predrainage and Excavating-Drainage Collaboration on Roadway Head

Table 2

Drilling layout parameters of different schemes.

	Borehole order	Predrainage					Excavating drainage
		1#	2#	3#	4#	5#	1#	2#	3#	4#	5#	6#
Scheme one	Angle between borehole and middle line of the roadway/°	0	0	0	0	0	0	1	2	4	6	7
	Drilling spacing/m	1.8					0.5
Scheme two	Angle between borehole and middle line of the roadway/°	0	0	0	0	0	0	0	0	0	0	0
	Drilling spacing/m	1.8					0.5
Scheme three	Angle between borehole and middle line of the roadway/°	0	0	0	0	0	1	3	5	7	9	11
	Drilling spacing/m	1.8					0.5
Scheme four	Angle between borehole and middle line of the roadway/°	0	0	0	0	0	0	1	2	4	6	7
	Drilling spacing/m	1.3					0.1
Scheme five	Angle between borehole and middle line of the roadway/°	0	0	0	0	0	0	1	2	4	6	7
	Drilling spacing/m	2.3					0.9