Crack Initiation Characteristics of Gas-Containing Coal under Gas Pressures

Table 1

Mean values of uniaxial compressive strength (), tensile strength (), and fracture toughness () of coal under different gas pressures.

Specimen	(MPa)	Average	∆ (%)	(MPa)	Average	∆ (%)	(MPa·m^1/2)	Average	∆ (%)
No gas
1	22.79	23.54	—	2.13	1.99	—	0.45	0.44	—
2	24.66			2.25			0.45
3	20.51			1.06			0.43
4	27.85			2.77			0.46
5	21.88			1.76			0.44
0.5 MPa
1	19.73	19.7	16.31	1.62	1.64	17.68	0.36	0.34	22.56
2	23.2			2.44			0.39
3	20.68			1.94			0.37
4	18.9			1.17			0.30
5	15.96			1.04			0.30
1.0 MPa
1	16.12	15.71	33.26	1.12	1.24	38.00	0.22	0.24	46.56
2	12.61			0.75			0.22
3	13.4			1.05			0.22
4	18.81			1.98			0.30
5	17.64			1.29			0.23
1.5 MPa
1	14.04	13.75	41.59	0.54	0.60	69.85	0.19	0.17	61.19
2	17.8			1.01			0.23
3	12.26			0.43			0.12
4	9.03			0.33			0.11
5	15.62			0.70			0.21