Energy Accumulation and Dissipation of Coal with Preopening under Uniaxial Loading

Figure 16

Macrofracture morphology of coal sample with different hole angle. (a) Intact coal specimen, (b) β = 0, (c) β = 30°, (d) β = 60°, and (e) β = 90°.

(a)

(b)

(c)

(d)

(e)