Spatial and Temporal Distribution Law and Influencing Factors of the Mining-Induced Deformation and Failure of Gas Boreholes

Table 2

Mechanical parameters of strata.

		Lithology		Coal	Mudstone	Siltstone	Sandstone
Strength parameters	Matrix	Peak value	Internal friction (°)	29	35	45	50
			Cohesion (MPa)	1.06	1.9	2.2	2.8
			Tensile strength (MPa)	0.03	0.42	0.68	1
		Residual value	Internal friction (°)	28	34	43	48
			Cohesion (MPa)	0.0106	0.19	0.22	0.28
			Tensile strength (MPa)	0	0	0	0
	Joint	Peak value	Internal friction (°)	25	30	42	45
			Cohesion (MPa)	0.8	1.5	2	2.5
			Tensile strength (MPa)	0.01	0.4	0.6	0.8
		Residual value	Internal friction (°)	24	29	38	43
			Cohesion (MPa)	0.008	0.15	0.2	0.25
			Tensile strength (MPa)	0	0	0	0
Stiffness parameters		Bulk modulus (GPa)		1.5	3.5	3.6	5.3
		Shear modulus (GPa)		0.3	1.6	2.2	4