Experimental Study on Crack Extension Rules of Hydraulic Fracturing Based on Simulated Coal Seam Roof and Floor

Table 1

Mechanical parameters of coal rock and roof-floor.

Rock formation	The compressive strength σc (MPa)		Modulus of elasticity (MPa)		Tensile strength σt (MPa)
	Sample	The average	Sample	The average	Sample	The average
Coal	6.24	6.47	1.186	1.195	0.94	1.09
	6.49		1.307		1.21
	6.68		1.092		1.13
Roof	15.58	15.95	2.661	2.636	2.92	3.22
	16.52		2.562		3.283
	15.76		2.684		3.458
Floor	18.76	18.91	2.947	2.942	4.011	3.58
	19.13		2.984		3.507
	18.85		2.895		3.224