Stability of Coal Pillar and Roof Movement Characteristics in Roadway Backfill Mining

Table 1

Physical and mechanical parameters of each rock formation.

Lithology	Density (kg·cm^3)	Tensile strength (MPa)	Cohesion (MPa)	Internal friction angle (°)	Bulk modulus (GPa)	Shear modulus (GPa)
Fine sandstone	2550	2.5	1.13	30	6.20	4.15
Medium sandstone	2500	2.4	1.12	30	6.17	4.07
Mudstone	2100	0.5	0.22	29	6	5
Coal	1400	1.2	2.0	28	1.94	0.80
Sandy mudstone	2200	0.6	1	28	0.63	0.5
Filling body	1100	1.2	1.3	29	0.9	1.4