Experimental Study on Triaxial Unloading Failure of Deep Composite Coal-Rock

Table 1

Preliminary test results.

Sample number	Height (mm)	Diameter (mm)	Confining pressure (MPa)	Compressive strength (MPa)	70% of compressive strength (MPa)
Pre-1#	101.640	49.540	10.000	51.997	36.398
Pre-2#	101.320	49.600	15.000	68.257	47.778
Pre-3#	101.520	49.640	20.000	80.929	56.650