Analysis of mechanical properties and acoustic emission characteristic of coal-rock assembly under the effect of size and shape

In order to study the influence of the mechanical properties and acoustic emission characteristics of the coal-rock assembly under the effect of size and shape, the uniaxial analysis of coal-rock assembly specimens of different sizes and shapes was carried out, and the acoustic emission system is used to record the ringing count and energy evolution of the internal acoustic emission of the specimen at different loading stages. The results show that the strength of the coal-rock assembly is between that of pure coal and pure rock. The peak strengths of the pure rock, pure coal, and coal-rock assembly specimens are 30.3 MPa, 5.7 MPa, and 9.7 MPa, respectively; the peak intensity of the combination body and the cubic combination body are continuously reduced with the decrease of the aspect ratio, and the maximum reduction amplitude is 52.68% and 59.21% respectively; the acoustic emission ringing count and energy of the specimens show consistent regularity, both of which show the trend of simultaneous change with the stress of the specimen; the appearance of the maximum ringing count of the cylindrical assembly is earlier than the appearance of the maximum stress value, while the maximum ringing count of the cubic assembly lags the appearance of the maximum stress value.