Acoustic Emission Experimental Research of the Damage Characteristics of Raw Coal under Different Loading and Unloading Rates

Table 1

Parameters of coal samples.

Number of experiment groups	Number	Strain rate (%/min)	Diameter (mm)	Height (mm)	Cell pressure (MPa)	Axial pressure (MPa)
First group	1	0.005	50.33	101.50	15	Load to destruction
	2	0.02	50.57	101.37
	3	0.03	50.43	101.35
Number of experiment groups	Number	Confining pressure unloading rate (MPa/s)	Diameter (mm)	Height (mm)	Cell pressure (MPa)	Axial pressure (MPa)
Second group	4	0.1	50.53	101.30	15	25
	5	0.2	50.33	101.35
	6	0.4	50.47	101.37
	7	0.6	50.53	101.43