Mechanical Properties and Energy Dissipation Characteristics of Coal–Rock-Like Composite Materials Subjected to Different Rock–Coal Strength Ratios

Abstract

The analysis of failure behaviors and energy dissipation characteristics of a coal–rock composite model is crucial to study mine dynamic disasters. A series of uniaxial loading and acoustic emission (AE) tests were implemented on coal–rock composite specimens with various rock–coal strength ratios (RCSRs). The results showed that the RCSR significantly affected the specimens' energy dissipation and mechanical characteristics. As the RCSR of the specimens increased, the failure mode of the rock–coal–rock specimens changed from shear failure to tensile failure. Based on the AE signal statistics, only one final failure occurred on the specimen with RCSR of 1:1, whereas the specimen with RCSR of 2:1–5:1 typically experienced coal failure first, followed by the final failure of the specimen. Energy dissipation and energy release are important causes of coal and rock damage. The energy dissipation coefficient curve had a significant peak value at the yield strength point, indicating that the dissipated energy began to increase quickly and that the specimen entered the unsteady failure stage with increasing loading. Moreover, the energy-storage limit and the final AE accumulative energy of specimens with different RCSRs showed that rock strength improved the specimens' non-deformability. The energy mechanism that drives crack growth and failure behavior was analyzed using energy theories and principles. The findings contribute to the study of coal and gas outbursts and dynamic disasters in coal mining activities.