An Experimental Study of the Uniaxial Failure Behaviour of Rock-Coal Composite Samples with Pre-existing Cracks in the Coal

Table 3

MFIS, energy index peak caused by the MFI, and MFIM.

No.	MFI, stress, and energy index	MFIS	MFIS/UCS	MFIM
A-1		45.21	97.13%	A macrotensile crack initiated from surface crack tip
A-2		31.41	84.46%	A macrocrack initiated from the middle part of original vertical surface crack
A-3		29.38	71.87%	A macromixed crack initiated from the lower part of the original vertical penetrative crack along with the formation of surface spalling
A-4		34.69	77.93%	Surface spalling at the bottom of the coal
A-5		20.62	71.12%	A macrofailure initiated from the original vertical penetrative crack accompanied by surface spalling failure