Gob-Side Entry Retaining Technology with Advanced Empty Hole Butterfly-Shaped Weakening in Three-Soft Coal Seam in China

Figure 20

Change curve of the observed roof to floor convergence: (a) No. 1 measurement point; (b) No. 2 measurement point; (c) No. 3 measurement point; (d) No. 4 measurement point; (e) No. 5 measurement point; (f) No. 6 measurement point.

(a)

(b)

(c)

(d)

(e)

(f)