Study on time-frequency-fractal characteristics of EMR signals and energy evolution during coal rock rupture at different loading conditions

• Published in: Journal of applied geophysics Vol. 241; p. 105823
• Main Authors: Sun, Xinyu, Li, Baolin, Wang, Enyuan, Li, Zhonghui, Cao, Xiong, Zhang, Meng
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2025
• Subjects: Coal and rock rupture; Different loading conditions; Electromagnetic radiation; Energy evolution; Response characteristics; Electromagnetic radiation; Different loading conditions; Energy evolution; Coal and rock rupture; Response characteristics
• ISSN: 0926-9851
• DOI: 10.1016/j.jappgeo.2025.105823

Electromagnetic radiation (EMR) monitoring technology has the advantages of non-contact testing, high sensitivity, and reflecting much information (stress, deformation, and rupture), which has the prospect of application in rock burst disaster monitoring. Defining the characteristics of EMR signals from coal-rock ruptures is the basis for the application of this technology. During the occurrence of rock burst, coal and rock will be loaded in different ways (uniaxial loading, cyclic loading, graded loading). There are differences in the rupture process of coal and rock at different loading conditions, and the EMR signals will also show different characteristics. However, the current EMR signal characteristics of coal rock loading process are mostly focused on the uniaxial loading time and frequency domain, and lacks the comparison and analysis of EMR characteristics at different loading conditions. Therefore, compression experiments at different loading conditions were designed to analyze the EMR signals in the time domain, frequency domain, and fractal analysis of the whole process of coal rock compression, and discussed the process of energy evolution. The results show that: before coal-rock damage, in the time domain, the EMR energy and counts in general show a “sudden change type” or “slowly rising type”, which is highly correlated with the energy dissipation rate, and the dissipative energy is proportional to the average EMR energy; in the frequency domain, the center frequency will be shifted to the low frequency. Coal center frequency varies more widely at uniaxial loading and decreases less at cyclic and graded loading. The more violent the coal rock rupture is, the lower the center frequency is; in the fractal, ∆α shows a gradual increase or a sudden increase before coal-rock damage. The overall ∆α of coal is the highest at uniaxial loading, and ∆α is close to the same at the cyclic and graded loading. Rock usually has lower ∆α than coal, and similar in size regardless of the loading conditions. Coal rock rupture EMR time-frequency-fractal multi-parameter co-characterize of its response is more comprehensive. •Comprehensive analysis of time, frequency - domain and fractal characteristics of EMR signals during coal rock rupture under different loadings.•By integrating the time, frequency and fractal multi-parameters of EMR response during coal and rock rupture process for joint characterization.•Energy dissipation differences during coal rock rupture at different loadings were analyzed, along with the correlation between dissipated energy and EMR signal energy.