Experimental Research on Permeability of Coal and Rock Mass considering Postpeak Failure

Table 2

Gas permeability test data and calculation results.

Specimen	Unloading step size	Permeability at different confining pressures (×10^-5 m^2)
		5 MPa	4 MPa	3 MPa	2 MPa	1 MPa
Sandstone 1	1.0 MPa	0.68	1.14	1.70	2.25	4.83
Coal specimen 1	1.0 MPa			0.97	1.06	5.22
Sandstone 2	0.5 MPa	3.01	4.17	5.72	9.95	22.8
Coal specimen 2	0.5 MPa			0.09	1.38	2.75
Coal specimen 3	0.3 MPa			2.62	7.23	29.5