Continuous–Discontinuous Element Numerical Modeling of Damage and Fracture Characteristics of a Loaded Coal

In preventing and controlling coal–rock dynamic disasters, the damage and fracture characteristics of the loaded coal play an important role. Using the continuous–discontinuous element coupling numerical software and the experimental test results of the acoustic emission (AE) of the loaded coal, the damage and fracture modes as well as the evolution laws of crack propagation of coal under uniaxial compression were thoroughly analyzed in this study. The results showed that the physical and mechanical properties, such as uniaxial compressive strength, have no bearing on the generation of AE signals, which are only related to the number and expansion evolution laws of cracks in the loaded coal. The mode of internal crack propagation in loaded coal is influenced by its uneven stress distribution, and the interior of loaded coal frequently develops a mixture of multiple crack types, as opposed to a single type. Besides, the system’s unbalanced rate in power and heating transmission systems was incorporated into the damage and fracture analysis of loaded coal, and it varied with the degree of fracture development in coal, which can be used as alternative expression method of damage variable under specific conditions. The main fracture surface’s propagation direction was also affected by the initial crack’s location, as demonstrated by the numerical simulation results. To compensate for the limitations of conventional testing methods, we developed a numerical model that recreates the internal cracks’ spatio-temporal evolution process and elucidates the damage fracture modes and the evolution laws of crack propagation in the loaded coal.