Fractal Characteristics of Coal and Sandstone Failure under Different Unloading Confining Pressure Tests

Table 3

Results of triaxial unloading confining pressure tests.

Lithology	σ3 (MPa)	(MPa/s)	σ1–σ3 (MPa)	σ3′ (MPa)
Coal	4	0.02	31.74	2.30
	4	0.05	30.02	0.63
	4	0.08	26.99	0.61
	7	0.02	37.23	4.39
	7	0.05	36.04	3.84
	7	0.08	36.26	1.63
	10	0.02	52.06	6.13
	10	0.05	50.21	4.58
	10	0.08	44.44	4.58
	10	0.11	45.42	1.57
	10	0.14	43.51	1.40
Sandstone	4	0.02	135.27	1.24
	4	0.05	132.95	0.01
	4	0.08	124.01	0.01
	7	0.02	138.89	4.36
	7	0.05	136.36	1.88
	7	0.08	125.75	0.00
	10	0.02	151.60	7.25
	10	0.05	141.05	4.99
	10	0.08	138.63	2.75
	10	0.11	132.77	2.70
	10	0.14	132.21	0.00
	13	0.05	149.93	6.82
	16	0.05	159.42	8.69
	19	0.05	180.97	11.56