Disastrous Mechanism of Water Discharge in Abandoned Gob above the Stope in Mining Extra-Thick Coal Seam

Table 1

The physical parameters of rock mass.

Rock strata	K (GPa)	G (GPa)	d (N·m^-3)	f (°)	C (MPa)	t (MPa)
Coal seam	3.89	1.59	1426	42	2.01	1.6
Sandy mudstone	30.35	14.74	2693	35	12.5	4.4
Siltstone	18.50	16.02	2604	34	4.8	4.89
Fine sandstone	19.79	19.86	2700	34	4.8	6.4
Medium sandstone	23.24	15.93	2654	35	12.5	5.72
Coarse sandstone	10.85	7.5	2540	35	12.5	2.56