Table 1. Parameters for Calculation.

parameter	symbol	value
initial gas pressure	p0	1.0 × 106 Pa
initial gas density	ρ0	18.87 kg/m3
atmospheric pressure	pa	0.1 × 106 Pa
gas density (standard atmospheric pressure)	ρa	1.977 kg/m3
vertical in situ stress	q1	2.5 MPa
horizontal in situ stress	q2	2.0 MPa
permeability of the coal sample	K	6.243 × 10–12 m2
porosity of the coal sample	φ	10%
dynamic viscosity of the gas	μ	1.35 × 10–5 Pa·s
specific heat ratio of the gas	γ	1.29
width of the orifice	D	30 mm
length of the model	l	1050 mm
half the height of the model	h	205 mm
elastic modulus of the coal sample	E	300 MPa
Poisson’s ratio of the coal sample	υ	0.3
cohesion of the coal sample	C	0.73 MPa
internal friction angle of the coal sample	ψ	35°
density of the coal sample	ρs	1380 kg/m3
diameter of the coal particle	d	5 mm
gas adsorption constant	A	0.024 m3/kg
gas adsorption constant	B	0.96 MPa–1
temperature	T	298.15 K
molar gas constant	R0	8.3143 J/(mol·K)
molar volume	Vm	22.4 × 10–3 m3/mol