Analysis of the Progressively Enhanced Mine Pressure in the Fully Mechanized Top Coal Caving Work Face of a 20 m Ultra-Thick Coal Seam

Figure 4

Evolution of the overlying rock strata during work face advancing. (a) 64 m. (b) 105 m. (c) 140 m. (d) 202 m.

(a)

(b)

(c)

(d)