Influence Law of Interbedded Strata and Their Collapse on the Mining of Extremely Thick Coal Seam under Goaf

Table 4

Traditional empirical calculation formula of collapsed and fractured zone height.

Lithology	Maximum height of caving zone (m)	Maximum height of fracture zone (m)
Hard rock
Medium-hard rock
Soft stratum
Extremely weak rock

M: thickness of the coal seam; ± is the margin of error.