Mechanism and Control of Water–Rock Coupling-Induced Disaster when Mining below the Unconsolidated Confined Aquifer

Table 2

Mechanical parameters of the joint.

Lithology	(GPa)	(GPa)	(MPa)	(°)
Middle water-resisting layer	3.5	1.8	0.12	8
Lower confined aquifer	2.0	1.2	0.08	5
Lower water-resisting layer	3.5	1.8	0.12	8
Overlying strata	4.0	2.0	0.20	8
Main roof	11.0	6.1	0.78	15
Coal seam	5.0	3.7	0.25	10
Immediate floor	7.5	4.4	0.46	12
Main floor	11.0	6.1	0.78	15
Underlying strata	14.0	8.7	0.65	18

: normal stiffness; : shear stiffness; : cohesion of joint; and : friction angle of joint.