Control of the Internal and External Staggered Distance of Coal Mining Face to the Water-Conducting Fissures in the Overlying Strata of the Near Coal

Table 2

The mechanical parameters of rock.

Rock formation	Density d (kg·m^−3)	Bulk modulus k (GPa)	Shear modulus (MPa)	Cohesion c (MPa)	Internal friction angle f (°)	Tensile strength σt (MPa)
Coal seam	1400	2.3	2	1.25	27	0.6
Silt sandstone	2420	30.3	13	9.6	33	6
Coarse-grained sandstone	2480	19	12.1	4.3	32	6
Medium-grained sandstone	2500	37.5	19.5	4.3	33	3.2
Fine-grained sandstone	2510	40.8	20.2	4.3	33	3.2
Sandy mudstone	2410	6.3	6.9	6.7	31.5	2
Loess	1720	20	14.2	3	15	4.3
Loose layer	2200	14	11.5	10	32	2