Analysis of Overburden Structure and Pressure-Relief Effect of Hard Roof Blasting and Cutting

Table 1

Physical and mechanical parameters of coal and roof.

Lithology	Thickness (m)	Density (kN·m^−3)	Modulus of elasticity (GPa)	Poisson’s ratio	Tensile strength (MPa)	Internal friction angle (°)	Note
Coal seam	3	13.5	2.2	0.43	0.41	14.8
Siltstone	9.07	24.1	22	0.27	4.2	32	Main roof
Sand shale interbed	8.93	25.7	15.6	0.29	3.7	31	Compensated load