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| Symbol | Definition and units |
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| Porosity of coal fracture |
| Gas pressure in coal fracture (MPa) |
| The radial distance in coal matrix (m) |
| Fracture permeability (md) |
| Permeability coefficient of fracture (m2/(MPa2·s)) |
| Dynamic viscosity of mixed gas (Pa·s) |
| Universal gas constant (8.314 J/(mol·K)) |
| Temperature of coal mass (K) |
| Molar mass of mixed gas (kg/mol) |
| The pressure at standard condition (0.101325 MPa) |
| Methane density at standard condition |
| Gas mass transfer item (m3/(m3·s)) |
| Methane density in coal matrix (kg/m3) |
| Flow coefficient in matrix density flow (m5/(kg·s)) |
| Radius of coal matrix (m) |
| Cleat compressibility (1/MPa) |
| Initial permeability coefficient of fracture (m2/(MPa2·s)) |
| Poisson’s ratio |
| Young’s modulus (MPa) |
| , | Matrix shrinkage constant (MPa; dimensionless) |
| Initial gas pressure in coal (MPa) |
| Coal density (kg/m3) |
| Density of adsorbed methane (kg/m3) |
| Porosity of coal matrix (dimensionless) |
| Mass of free methane per unit coal matrix (kg/kg) |
| Air pressure in roadway space(MPa) |
| Borehole drainage pressure (MPa) |
| Langmuir sorption constants (m3/kg; 1/MPa) |
| Methane pressure in coal fracture (MPa) |
| Air pressure in coal fracture (MPa) |
| Methane molar mass (kg/mol) |
| Length of drainage borehole (m) |
| Sealing length of the borehole (m) |
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