The Study of Key Stratum Location and Characteristics on the Mining of Extremely Thick Coal Seam under Goaf

Figure 2

The evolution diagram of collapsing characteristics of overburden rock in 35 m interlayer: (a) advance of the working face 40 m; (b) advance of the working face 60 m; (c) advance of the working face 80 m; (d) advance of the working face 100 m; (e) advance of the working face 140 m; (f) advance of the working face 180 m.

(a)

(b)

(c)

(d)

(e)

(f)