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

Table 1

Acoustic wave test results of typical rock specimens.

Lithology	Number	P-wave velocity (m/s)	S-wave velocity (m/s)
Coal	16-N-18	1932.746	1005.961
	16-N-17	1990.223	1192.537
	16-M-17	1946.301	1072.167
	16-M-19	1972.257	1153.173
	16-M-10	1988.963	1014.426
	16-M-14	1944.138	1051.107
	16-N-16	1896.321	1062.36
	16-N-20	1957.746	1051.003
	16-N-9	1919.274	1134.921
	16-1-8	1981.991	975.2184
	16-1-1	1942.238	948.1264
Sandstone	S-7-5	4891.536	2234.588
	S-7-1	5021.928	3076.94
	S-7-3	4828.032	2559.21
	S-2-6	5214.408	2908.235
	S-2-11	4990.176	2664.642
	S-5-2	5239.656	2856.324
	S-2-4	5418.984	2895.125
	S-2-10	5296.032	3008.285
	S-1-5	5060.28	3095.432
	S-5-6	5173.08	2682.26
	S-5-13	4856.928	2458.953