Temporal and spatial evolution of acoustic emission and waveform characteristics of specimens with different lithology

Through the acoustic emission (AE) test of gypsum, coal, concrete and sandstone specimens under uniaxial compression, the load axial deformation curves and AE parameters of four kinds of specimens with different lithology are obtained. The temporal and spatial evolution law of AE and the multifractal characteristics of the waveform before and after rupturing are analyzed. The results show that the uniaxial compressive strength of gypsum, coal, concrete and sandstone specimens increases in turn; the AE pulsing counts of the four specimens are consistent with stress changes, moreover, the maximum AE pulsing counts of gypsum, coal, concrete and sandstone specimens increase in turn; the spatial location of the four specimens is consistent with their macroscopic rupturing morphology, but the time of occurrence and the location of the distribution are different; the rupturing waveforms of the four specimens have multifractal characteristics, the multifractal spectrum Delta f(alpha) of the four specimens when rupturing is smaller than that of Delta f (alpha) before rupturing, and the Delta f(alpha) before rupturing is smaller than that of Delta f(alpha) after rupturing, the Delta f(alpha) of gypsum, coal, concrete and sandstone specimens decreases at the corresponding stages. It is shown that the energy of the four specimens when rupturing is larger than that before rupturing, and the energy before rupturing is larger than that after rupturing, moreover, the energy of gypsum, coal specimen, concrete and sandstone specimens increases at the corresponding stages, this is consistent with acoustic emission pulse counts. The biggest rupturing moment gradually increased from gypsum, coal, concrete to sandstone. Through the analysis of temporal and spatial evolution law of AE and the multifractal characteristics of the waveform of four kinds of specimens with different lithology, to further understand the law of rupturing, and lay a theoretical foundation for the prevention and control of rock burst in coal mine.