Goaf Gas Control Improvement by Optimizing the Adjacent Roadway Large-Diameter Boreholes

Table 1

Calculation formula parameters’ values.

Symbol	Parameter	Value	Unit
a/b/c	Calculation parameters of the fracture zone	1.5/3.6/5.6
H	Mining height	5.2	m
hd	Thickness of immediate roof	6	m
Kpb	Coefficient of rock crushing expansion of the caving zone	1.049
l	Length of main roof broken rock block	8	m
l1	Strike length of working face	185	m
l2	Strike length of goaf	185	m
m	Thickness of mining seam	5.2	m
q0	Gas emission intensity of coal wall	0.0503	m^3·(m^2·min)^−1
	Advancing speed of the working face	4.2 × 10^−3	m·min^−1
	Original gas content of coal seam	12.1	m^3·t^−1
	Residual gas content	2.81	m^3·t^−1
α	Coal seam dip angle	0	°
λ	Gas emission coefficient	1.34