Study of the Stability Control of the Rock Surrounding Double-Key Strata Recovery Roadways in Shallow Seams

Table 1

Physical and mechanical parameters of the coal stratum.

Rock formations	Density (kg·m^−3)	Friction angle (°)	Tensile strength (MPa)	Shear modulus (GPa)	Bulk modulus (GPa)	Cohesion (MPa)
Unconsolidated stratum	1760	20	0.1	0.0071	0.0125	0.019
Coarse sandstone	2586	43	11.5	14.0	18.0	3.8
Mudstone	2545	30	1.8	2.8	4.3	0.7
Pelitic siltstone	2540	35	1.0	1.6	2.7	2.0
Peat mudstone	2699	39	2.5	2.8	2.9	1.4
Medium coarse sandstone	2590	36	6.0	22.0	18.7	12.1
Silty mudstone	2500	32	1.0	1.0	2.0	2.8
#2 coal seam	1380	32	0.5	2.3	5.0	1.3
Medium sandstone	2530	29	2.0	4.7	7.5	7.5
#3 coal seam	1390	28	0.5	2.3	5.0	1.0
Pelitic siltstone	2650	38	1.8	4.9	10.8	2.8