Study on Test Method of Rock Acoustic Emission and Damage Evolution Characteristics Under Triaxial-Compression

Aiming at the disadvantages of being unable to detect the comprehensive and reliable acoustic emission(AE) signals with acoustic emission detector installed outside the triaxial chamber, reasonable test method is realized with the AE detector installed inside the triaxial chamber based on the communication interface refitting of MTS815 rock mechanical test system. Based on reasonable test method, compression fracture AE tests of coal specimens are carried out under different confining pressure. Compared with uniaxial compression test, the primary fractures inside specimens are relatively compressed to close by confining pressure, the AE activities decrease in the stage of compaction; at the same time, the time that the AE counts and the energy reaching their highest values are both relatively lag behind the transient time of the macroscopic failure of coal specimens, it shows that confining pressure improves not only the peak strength, but also the bearing capacity. Based on AE characteristics of coal specimens under the triaxial compression, the evolution process of triaxial compression failure can be simplified into four stages as compaction and elasticity, plastic failure, failure and its development, plastic flow.