Experimental Investigation on the Propagation of Hydraulic Fractures through Coal-Rock Interfaces

Table 2

Hydraulic fracturing simulation experimental program on combination samples.

Combination sample	Sample no.	Fracture initiation position	Raw coal-rock size/mm	Stress/MPa			Triaxial pressure diagram
			Length × width × thickness
Two-dimensional coal-rock combination plate	1#	Concrete	208 × 102 × 49	3.5	4	2
	2#	Concrete	210 × 100 × 50	3.5	4	2
	4#	Concrete	195 × 95 × 50	3.5	4	2
Large-scale cubic coal and rock mass	1#	Sand mudstone	270 × 135 × 150	4.7	6.8	2.8
	3#	Coal	220 × 100 × 200	4.7	6.8	2.8
	4#	Sand mudstone	270 × 172 × 158; 270 × 170 × 75 (coal)	4.7	6.8	2.8