Hydraulic Fracture Propagation and Permeability Evolution in the Composite Thin Coal Seam

Table 1

Parameters of RFPA^2D-Flow simulation.

Parameters	Values	Parameters	Values
Uniaxial compression strength of coal seam	20 MPa	Horizontal principal stress	3 MPa
Uniaxial compression strength of gangue strata	35 MPa	Evenness of coal	1000
Elastic modulus of coal seam	50000 MPa	Evenness of gangue strata	1000
Elastic modulus of gangue strata	70000 MPa	Internal friction angle	30°
Weight	N/mm^3	Residual strength	0.1%
Ratio of compression strength to tensile strength	10	Coefficient of pore pressure in the coal	0.1
Initial permeability coefficient of coal	0.0008 m/D	Coefficient of pore water in the gangue	0.1
Initial permeability coefficient of gangue strata	0.0006 m/D	Maximum compressive strain coefficient	200
Maximum tensile strain coefficient	1.5	Increased injection pressure at each step	0.2 MPa
Initial injection pressure	3 MPa	Vertical principal stress	6 MPa