Acoustic emission characteristics of coal specimen under triaxial cyclic loading and unloading

By using RMT-150B rock mechanics test equipment, the acoustic emission (AE) tests of coal specimen under conventional triaxial and triaxial cyclic loading and unloading were carried out, and AE characteristics of coal specimens under different loading situations was analyzed. The test results show that the AE mutation point in conventional triaxial compression process is substantial in about 85% of the peak stress, and AE count more accusatively responses to AE information in coal specimen deformation and failure process, which can be used as a precursor to determine the coal specimen failure. AE information occurs in the interval of cyclic loading and unloading process, and the change trends of energy, count and amplitude are same and coincide with the stress of the coal specimens. Felicity effect in the cyclic loading and unloading process is obvious, and the Felicity ratio FR is much less than 1.That the FR value continuously decreases with the cyclic stress level increasing shows the advance feature of AE memory in the cyclic loading and unloading process. The memory effect of Kaiser effect is poor, and Kaiser effect as the coal body stability index needs to be cautious.