Study on Influence Laws of Strata Behaviors for Shallow Coal Seam Mining beneath Gully Terrain

Table 2

Mechanical parameters of strata.

Rock stratum	Thickness (m)	Density (kg·m^−3)	Bulk modulus (GPa)	Shear modulus (GPa)	Cohesion (MPa)	Internal friction angle (°)	Tensile strength (MPa)
Loose layer	60	2000
Sandy mudstone	19	2450	2.3	2.1	1.8	32	1.3
Siltstone	27	2550	3.4	3.1	2.6	31	1.4
Feldspar sandstone	22	2500	3.1	3.0	2.5	30	1.1
Siltstone	24	2550	3.4	3.1	2.6	31	1.4
Feldspar sandstone	21	2500	3.1	3.0	2.5	30	1.1
Siltstone	18	2450	2.3	2.1	1.7	29	0.6
Feldspar sandstone	3	2550	3.4	3.1	2.6	31	1.4
No. 3 coal seam	3	1333	2.5	2.3	0.4	29	0.7
Siltstone	7	2550	3.3	3.0	2.7	31	1.4
Feldspar sandstone	19	2500	3.2	3.1	2.6	32	1.1