Study on Acoustic Emission Characteristics and Crack Evolution Characteristics of Conglomerate Under Uniaxial Compression

Taking the giant thick conglomerate in Yima mining area as the research background, this paper investigates the acoustic emission characteristics and crack evolution law of conglomerate with different grain sizes under loading conditions through uniaxial compression test and acoustic emission (AE) technology, and discusses the influence of grain size on its damage mechanism and damage evolution. The results show that : the AE energy and ringing counts of conglomerate specimens increase significantly with the increase of grain size, and large-grained conglomerates show stronger shear damage characteristics during the damage process; Specimens with larger grain sizes have a higher rate of AE events during the damage process, whereas those with smaller grain sizes show a lower damage variable D and higher load-bearing capacity after the damage intensity; During the whole process of rock damage, the AF value shows the evolution law of first fluctuation, then decrease, and a small increase near the damage, while the RA value is overall lower, and rises sharply near the damage, indicating that the change of AF and RA values can be used as a precursor indicator of rock destabilization damage; The crack extension form evolves significantly with the loading process, with tensile and shear cracks predominating before the initiation of the fracture strength, and shear cracks predominating near the destabilization damage. Shear cracks dominate near the destabilizing damage. The shear crack surge stage of medium and coarse grain specimens with larger grain size appeared after the crack initiation strength, while the shear crack surge stage of fine grain specimens with smaller grain size appeared after the damage strength. The results reveal the acoustic emission characteristics and crack evolution laws of conglomerates with different grain sizes during the damage process, deepen the understanding of the mechanical behavior and damage mechanism of conglomerates, and provide theoretical basis and technical support for the stability evaluation of the giant conglomerate strata in the Yima Mining Area and the prediction of engineering disasters.