Experimental Study on AE Characteristics of Natural and Water-saturated Coal in Process of Deformation and Fracture

In this paper, we use the experimental system to test the AE signals of natural and water-saturated coal samples during the process of deformation and fracture under uniaxial compression; their characteristics including AE signals pulse, energy and dominant frequency in the whole loading stages were analyzed. In addition, we summarized the precursory characteristics of AE signals in the process of coal deformation and fracture. The results suggest that the pulse and energy of AE signals of natural and water-saturated coal samples are both less in compression phase; the frequency bands of both are wider, the dominant frequency is not obvious and the amplitude of dominant frequency is less; in elastic stage, the pulse, energy and dominant frequency of AE signals of natural coal show a fluctuant rise, while not until middle and later elastic stage make the AE signals of water-saturated coal begin to appear clearly, and then the dominant frequency of AE also has a rising tendency; in the elastic-plastic stage, the AE signals pulse and energy of both have the relatively quiet period, however, the quiet period of water-saturated coal appears comparatively late and has a shorter duration, in this stage, the dominant frequency of AE signals gradually moves to low frequency, but the amplitude of dominant frequency sharply increases and then decreases.