Research on the Reasonable Width of the Waterproof Coal Pillar during the Mining of a Shallow Coal Seam Located Close to a Reservoir

Table 2

Physical and mechanical parameters of the 4⁻² coal seam overlying strata.

Lithology	Thickness (m)	Buried depth (m)	Density (g/cm^3)	UCS (MPa)	Elastic modulus (GPa)	Poisson’s ratio	Tensile strength (MPa)	Cohesion (MPa)	Friction angle (°)
Sandy soil	5	5	1.92					0.046	29
Laterite	20	25	2.28					0.35	30.5
Mudstone	2.5	27.5	2.35	35.4	3.5	0.32	1.2	2.56	32.6
Fine-grained sandstone	4.5	32	2.67	50.4	4.3	0.24	3.5	4.02	39.8
Mudstone	5.5	37.5	2.35	35.4	3.5	0.32	1.2	2.56	32.6
Fine-grained sandstone	27.3	64.8	2.69	79.7	6.5	0.2	3.7	5.87	38.2
Siltstone	2.2	67.0	2.7	71.9	5.4	0.19	2.6	6.72	38
4^−2 coal seam	3.5	70.5	1.28	16.4	3.7	0.30	1.37	3.72	33.6
Fine-grained sandstone	25.4	95.9	2.69	79.7	4.3	0.2	3.7	5.87	38.2
Mudstone	16.1	112	2.35	35.4	3.5	0.32	1.2	2.56	32.6