Study on Evolution Characteristics of Regenerated Roof Structure in Downward Mining of Bifurcated Coal Seam

Table 2

Measured height of each zone in stope.

Borehole number	Distance between coal seams (m)	Thickness of floor damage zone (m)	Thickness of failure zone for floor (m)	Height of caving zone (m)	Height of fracture zone (m)
No. X1	7.30	1.17	6.13	12.40	36.10
No. X2	4.50	—	4.50	8.85	33.75
No. X3	4.20	—	4.20	5.70	32.10
No. X4	5.78	—	5.78	4.47	31.95
No. X5	8.13	1.93	6.20	5.22	33.58
No. X6	8.38	1.83	6.55	7.06	37.43
No. X7	7.20	1.20	6.00	11.95	38.88