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

Table 1

The mechanical properties of the coal-rock and concrete.

Combination sample	Remarks	Average tensile stress/MPa	Average elastic modulus/GPa	Average Poisson’s ratio	Average KIC/MPa.m^1/2
15# coal		1.50	0.66	0.28	0.16
		1.84	3.48	0.23	0.23
Sandy mudstone		3.17	6.58	0.19	1.12
		11.86	10.52	0.14	1.84
Concrete	Mass ratio 1 : 1	2.95	3.36	0.21	0.27
	Mass ratio 1 : 1.5	2.04	2.81	0.24	0.19