Research on mechanical properties and acoustic emission characteristics of rock beams with different lithologies and thicknesses

The lithology and thickness of the rock beam affect its mechanical properties and acoustic emission characteristics when it is fractured. In this study, three-point bending tests of rock beams were carried out. Then, we proposed to utilize the percentage of peak energy to characterize the intensity of energy release during fracture. Finally, the energy release mechanism of coal roof fracture was discussed. The evolution process of acoustic emission includes five stages. The acoustic emission amplitude distribution of rock beams has three typical patterns. Most of the cracks after fracture are tensile cracks, the proportion of tensile cracks is positively correlated with the elastic modulus. The percentage of peak energy is positively correlated with thickness and elastic modulus. More energy is released when thick and hard roof fractures. When necessary, measures such as reducing the thickness or the strength of the roof could be taken to improve the safety of mining.