Investigation on the Ground Pressure Induced by Hard Roof Fracturing at Different Layers during Extra Thick Coal Seam Mining

Figure 4

Stress distribution during the overburden fracturing.

(a) Main roof fracturing for the first time

(b) KS1 fracturing for the first time

(c) KS2 fracturing for the first time

(d) KS3 fracturing for the first time

(e) KS4 fracturing for the first time

(f) KS5 fracturing for the first time