Acoustic Emission Experimental Research of the Damage Characteristics of Raw Coal under Different Loading and Unloading Rates

Figure 12

Comparison of theoretical and experimental curves of coal sample damage under different unloading rates. (a) 0.1 MPa/s unloading rate. (b) 0.2 MPa/s unloading rate. (c) 0.4 MPa/s unloading rate. (d) 0.6 MPa/s unloading rate.

(a)

(b)

(c)

(d)