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

Table 3

Mechanical parameters of similar materials for coal seam roof and floor.

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: sand : gypsum : cement = 1 : 1 : 1	3.7032	3.9776	2.1884	2.0577	0.4853	0.4590
	4.0124		1.8621		0.6027
	4.2171		2.1226		0.2891
Group B: sand : gypsum : cement = 5 : 1 : 3	2.1027	2.1465	2.0639	1.9401	0.3832	0.3868
	1.9683		1.8547		0.1649
	2.3685		1.9016		0.6124
Group C: sand : gypsum : cement = 4 : 1 : 5	3.1984	3.0597	2.2278	2.1210	0.8084	0.6167
	3.0861		1.9419		0.6431
	2.8947		2.1934		0.3986
Group D: sand : gypsum : cement = 4 : 2 : 5	4.2371	4.1549	2.6893	2.7184	0.5311	0.5105
	3.8935		2.7231		0.4893
	4.3341		2.7429		0.5112
Group E: sand : gypsum : cement =4 : 1 : 6	3.5975	3.6251	2.4512	2.3878	0.9513	0.6852
	3.7892		2.5297		0.7704
	3.4887		2.1824		0.3339
Group F: sand : gypsum : cement = 4 : 2 : 3	2.6231	2.5790	2.6015	2.6124	0.4152	0.4145
	2.3093		2.5974		0.4371
	2.8047		2.6384		0.3912