Reasonable Scope of Kilometer Drilling in Lower Layer of Extrathick Coal Seam: A Case Study of Tingnan Coal Mine, China

Figure 10

Vertical stress of the section along the trending direction (different advance length). (a) Working face advancing 20 m. (b) Working face advancing 60 m. (c) Working face advancing 100 m. (d) Working face advancing 140 m. (e) Working face advancing 180 m. (f) Working face advancing 200 m.

(a)

(b)

(c)

(d)

(e)

(f)