Comparative Study on Two Types of Nonpillar Mining Techniques by Roof Cutting and by Filling Artificial Materials

Table 1

Physical and mechanical characteristic parameters of an inclined coal seam work face.

Rock strata	Density (kg·m^3)	Elastic modulus (GPa)	Poisson ratio	Tensile strength (MPa)	Cohesion (MPa)	Friction angle (°)	Thickness (m)
Overlying rock	2600	3.34	0.30	2.32	2.05	30	142
Fine sandstone	2680	5.46	0.28	2.65	2.86	34	7
Siltstone	2350	1.29	0.35	1.79	1.72	27	7
Coal	1350	2.90	0.36	1.40	3.20	25	4
Siltstone	2300	1.15	0.33	1.54	1.40	27	2
Fine sandstone	2540	3.82	0.27	1.95	2.23	32	6
Medium sandstone	2620	3.35	0.29	2.32	1.97	31	32