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

Table 2

Mechanical parameters of coal briquette.

The ratio of solution	The compressive strength σc (MPa)		Modulus of elasticity (MPa)		Tensile strength σt (MPa)
	Sample	The average	Sample	The average	Sample	The average
Group A: pulverized coal : gypsum : cement = 1 : 1 : 1	2.7828	2.4591	0.5537	0.5687	0.3219	0.3538
	2.3263		0.8204		0.2968
	2.2681		0.3321		0.4426
Group B: pulverized coal: gypsum : cement = 5 : 1 : 3	1.2318	1.2405	0.4617	0.4279	0.2018	0.2086
	1.0377		0.4138		0.2243
	1.4521		0.4082		0.1996
Group C: pulverized coal : gypsum : cement = 3 : 1 : 3	3.5214	3.5091	0.4862	0.6201	0.4251	0.4356
	3.2367		0.7124		0.2784
	3.7693		0.6618		0.6032
Group D: pulverized coal : gypsum : cement = 2 : 2 : 1	4.0213	4.1204	0.8032	0.8177	0.5021	0.5139
	3.9827		0.5683		0.2218
	4.3571		1.0817		0.8179
Group E: pulverized coal : gypsum : cement = 5 : 1 : 2	0.9437	0.8061	0.3041	0.2881	0.2217	0.1452
	0.7824		0.2854		0.1126
	0.6921		0.2747		0.1013