Uniaxial Compression Creep Relaxation and Grading of Coal Samples via Tests on the Progressive Failure Characteristics

Table 1

Test results for coal samples subjected to uniaxial compression and step relaxation.

Position	Type	Coal number	/mm	/mm	/kg·m^−3	/m·s^−1	/MPa	/GPa	/GPa
Middle	Conventional uniaxial	MZ1	49.4	103.7	1478	1865	33.39	4.44	3.62	0.31
		MZ2	49.5	102.9	1482	1780	19.58	4.01	2.71	0.36
		MZ3	49.4	100.4	1476	1770	31.97	3.95	2.93	0.26
	Stepwise relaxation	MZ4	49.5	98.0	1437	1795	26.46	4.15	3.05	0.33
		MZ5	49.5	99.3	1470	1770	12.10	2.40	1.53	0.21
		MZ6	49.5	101.1	1438	1893	27.31	3.81	3.40	0.31
Higher stratification	Conventional uniaxial	MS1	49.30	104.10	1470	1882	15.16	3.49	2.17	0.23
		MS2	49.50	100.60	1479	1729	15.28	3.30	1.95	0.36
		MS3	49.50	101.50	1461	1774	17.43	3.33	1.95	0.34
	Stepwise creep	MS4	49.70	102.40	1471	1965	7.97	2.16	1.64	0.19
		MS5	49.50	100.90	1469	1755	8.42	2.04	1.20	0.21
		MS6	49.50	98.20	1483	1839	15.50	3.65	2.71	0.30