Table 1 Model parameter.

Modulus of elasticity/GPa

2.713

13.8

Poisson’s ratio

0.32

0.25

Initial cohesion/MPa

2.5

15

Angle of internal friction/(°)

35

40

Bulk density/(kg/m³)

1400

2500

Plastic flow stage cohesion/MPa

0.5

20

Initial penetration rate/md

1.05 ~ 1.25

–

Penetration rate surge factor

100

–

Initial fracture rate

0.007 ~ 0.01

–

Matrix porosity

0.045

–

Maximum adsorption strain

0.011

–

Adsorption of deformation stress/MPa

5.14

–

Ultimate adsorption of gas a/(mL/g^− 1)

32.12 ~ 42.78

–

Matrix expansion and deformation rate

0.1

–

Fracture compression coefficient /MPa^− 1

0.1395

–

Substrate adsorption time/d

11.7

–

Adsorption constant b/MPa^− 1

1.28 ~ 1.32

–

Coal firmness factor

0.42 ~ 0.56

–

Effective diffusion coefficient /s^− 1

2.26 × 10^− 6

–

Gas viscosity factor/(Pa·s)

1.84 × 10^− 5

–

Coal matrix bulk modulus /MPa

12.4

–

Ideal gas constant/(mol∙K)

8.31

–

Molar mass of methane/mol

16

–

Temperature (K)

327.5

–