Experimental Study on Strength, Acoustic Emission, and Energy Dissipation of Coal under Naturally and Forcedly Saturated Conditions

Table 3

P-wave velocity variation of three types of coal samples.

Type of coal sample	Sample ID	(m/s)	(m/s)	(%)	(m/s)	(m/s)	(m/s)	(m/s)
Natural	A1	1416	N/A	N/A	1449	N/A	87.55	N/A
	A2	1538	N/A	N/A
	A3	1374	N/A	N/A
	A4	1349	N/A	N/A
	A5	1566	N/A	N/A
Naturally saturated	B1	1416	1507	4.1	1499	1623	88.00	123.13
	B2	1538	1731	9.2
	B3	1374	1444	3.1
	B4	1566	1690	6.0
	B5	1600	1742	6.6
Forcedly saturated	C1	1515	2153	42.1	1434	2117	56.19	21.04
	C2	1470	2110	43.5
	C3	1353	2105	55.6
	C4	1434	2127	48.3
	C5	1397	2092	49.7

Note.  = P-wave velocity before soaking;  = P-wave velocity after saturating;  = increase rate of P-wave velocity;  = average value of ;  = average value of ;  = standard deviation of ;  = standard deviation of .