Effect of Mining Thickness on Overburden Movement and Underground Pressure Characteristics for Extrathick Coal Seam by Sublevel Caving with High Bottom Cutting Height

Figure 4

Evolution process of mining roof caving in coal with a thickness of 9 m. (a) 32 m, (b) 40 m, (c) 52 m, (d) 60 m, (e) 80 m, (f) 92 m, (g) 112 m, (h) 120 m, (i) 172 m, (j) 184 m, (k) 220 m, and (l) 256 m.

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

(i)

(j)

(k)

(l)