Due to the complexity of the strata, it is difficult to monitor and identify the disasters induced by rock fractures in the process of mining deep coal resources. This will seriously affect the safety and sustainable mining of coal. Therefore, it is necessary to understand the failure mechanisms and acoustic emission (AE) characteristics of different rocks. In this paper, uniaxial compression tests as well as simultaneous AE monitoring were carried out on four different rocks. The four rocks include yellow sandstone, white sandstone, marble and limestone. The mechanical properties, energy evolution and AE characteristics of different rocks were analysed. It is found that the AE response of rocks is closely related to the damage and fracture process. The more brittle the rock is, the less energy is dissipated before failure, and the less obvious the AE precursor is, and the RA-AF values can effectively characterise the failure modes of different rocks. Finally, the damage models were developed from the perspectives of AE energy and dissipated energy, respectively. The damage model based on dissipated energy can better reflect the stress and damage state of the rock, and the theoretical curves of stress–strain are in good agreement with the measured curves.

In this study, uniaxial compression tests and simultaneous acoustic emission (AE) monitoring were carried out on four rocks (yellow sandstone, white sandstone, marble and limestone). The mechanical properties and AE energy evolution characteristics of different rocks were analysed. With the help of critical slowing down (CSD) theory, the AE precursor characteristics of their failure were investigated. It is pointed out that the AE during rock loading has a CSD phenomenon. A sudden change in the variance of one of the CSD indicators can be regarded as a precursor to failure, and it has the advantage of being more accurate and sensitive to failure than the autocorrelation coefficient. The stress level of a rock's failure precursor is closely related to its brittleness characteristics. The higher the brittleness of the rock, the more backward the failure precursor is, and the more difficult the early warning is. The study aims to provide new indicators and references for the monitoring and early warning of rockbursts and other disasters induced by rock fracture in deep underground engineering.

With the continuous increase of mining depth, coal and gas outburst poses a significant threat to mining safety. Conducting research on the mechanisms of coal and gas outbursts contributes to understanding the evolutionary process of such incidents, thus enabling accurate prediction and prevention of coal and gas outbursts during mining operations. This paper has developed a comprehensive visual experimental system that is specifically tailored to simulate diverse coal body conditions, ground stress and gas pressures. By monitoring and analyzing the real-time progression of coal fissures during the outburst process, we can obtain valuable insights into the evolution and mechanisms of coal and gas outbursts. Additionally, this study introduces a method to determine the critical threshold for predicting coal and gas outbursts, and the critical gas pressure threshold for Jiulishan Coal Mine (Jiaozuo City, Henan Province, China) is established at 0.6 MPa.

The occurrence of rock burst hazards is closely related to the brittleness of rocks. Current research has paid less attention to the in-depth relationship between rock brittleness and acoustic emission (AE) signal characteristics and precursor information caused by rock fracture. Therefore, in order to further improve the accuracy of the AE monitoring of rockburst hazards, uniaxial compression tests were carried out and AE were monitored for rocks with different brittleness (yellow sandstone, white sandstone, marble, and limestone) in this paper. The relationship between the mechanical properties and the time-frequency characteristics of the AE was analyzed. In addition, the multi-fractal theory was introduced to further deconstruct and mine the AE signals, and the multi-fractal characteristics of AE from rocks with different brittleness were investigated. The results show that the stronger the brittleness of the rock, the higher the main frequency and main frequency amplitude of the AE. Brittleness is positively correlated with the multi-fractal parameter Δα (uniformity of data distribution) and negatively correlated with Δf (frequency difference between large and small data). In addition, the dynamics of Δα and Δf provide new indicators for AE monitoring of rock stability, and their abrupt changes can be regarded as precursors of failure. The weaker the brittleness of the rock, the earlier the failure precursor is and the more significant it is. This has potential engineering application value, which can help identify rockburst precursors and take timely protective measures to ensure engineering safety.

In recent years, with the continuous increase in the depth and intensity of coal mining, coal and gas outburst disasters pose a severe threat to the safe production of coal mines. Thus, this experiment studied the characteristics of electromagnetic radiation, acoustic emission, and electric potential signals during gas adsorption, stress loading, and the entire outburst process. The results indicate that during the adsorption process, different parts of the coal body exhibit variations in electric potential signals, electromagnetic radiation, and acoustic emissions. During the loading process, the consistency between the acoustic–electric signals and the load change rate is good, and at the moment of outburst, the acoustic–electric signals significantly increase with the ejection of coal and gas. Outbursts generally occur during the decline in electromagnetic radiation and acoustic emission signals, with the internal electric potential signal strength first decreasing then rapidly increasing and the surface electric potential directly rising. The closer to the outburst opening, the greater the change in signal amplitude. Based on the above experimental results, the outburst can be monitored through the acoustic–magnetic–electric precursory signal changes during the adsorption and loading processes, which is of great significance to the safety production and rapid excavation of coal mines.