Mechanical Characteristics of Coal Samples under Triaxial Unloading Pressure with Different Test Paths

Table 2

Test data of different initial unloading confining pressure and confining pressure unloading rates.

Lithology	σ3 (MPa)	σ3 (MPa/s)	σ1 −  (MPa)	Residual strength (MPa)	(MPa)	σ3 −  (MPa)	ε3 (mm/mm)	ε1 (mm/mm)	(mm/mm)
Coal	4	0.02	30.82	16.06	2.28	1.72	−0.00205	0.00462	0.00053
	4	0.05	29.15	12.54	0.62	3.38	−0.00165	0.00394	0.00064
	4	0.08	26.20	13.17	0.60	3.40	−0.00121	0.00372	0.00130
	7	0.02	36.15	20.46	4.35	2.65	−0.00262	0.00570	−0.00034
	7	0.05	34.99	19.72	3.80	3.20	−0.00173	0.00439	0.00093
	7	0.08	35.20	15.60	1.61	5.39	−0.00143	0.00395	0.00060
	10	0.02	50.54	24.34	6.07	3.93	−0.00285	0.00687	0.00116
	10	0.05	48.75	15.68	4.53	5.47	−0.00268	0.00610	0.00074
	10	0.08	43.15	17.49	4.53	5.47	−0.00228	0.00562	0.00107
	10	0.11	44.10	11.33	1.55	8.45	−0.00211	0.00525	−0.00134
	10	0.14	42.24	8.45	1.39	8.61	−0.00205	0.00514	0.00025