Aquiclude Stability Evaluation and Significance Analysis of Influencing Factors of Close-Distance Coal Seams: A Case Study of the Yili No. 4 Coal Mine in Xinjiang, China

Table 4

Physical and mechanical parameters of the overlying rocks.

Lithology	Density (kg m^-3)	Bulk modulus (GPa)	Shear modulus (GPa)	Internal friction angle (°)	Cohesion (MPa)	Tensile strength (MPa)
Silt	1240	0.4	0.2	13	0.1	0.08
Gravel	1240	0.6	0.3	23	0.4	0.24
Mudstone	2300	1.0	0.7	20	1.1	0.62
Sandstone	2200	1.2	0.9	30	0.9	0.50
Sand mud interbed	2500	1.2	0.7	23	0.8	0.36
21-1 coal	1240	1.1	0.6	20	0.3	0.32
Mudstone	2430	1.0	0.7	20	0.6	0.42
23-2 coal	1240	1.1	0.6	20	0.3	0.32
Sandstone	2600	2.5	1.8	30	1.3	1.20