Stability Control Mechanism of High-Stress Roadway Surrounding Rock by Roof Fracturing and Rock Mass Filling

Figure 7

Photographs of a coal pillar with different borehole depths obtained by a rock layer detection recorder. (a) Borehole depth of 2 (m). (b) Borehole depth of 4 m. (c) Borehole depth of 6 m.

(a)

(b)

(c)