Characterization of mesoscopic damage evolution in complex calcite vein-filled coal rocks

To investigate the failure characteristics of calcite veins with complex morphologies in coal rock under uniaxial compression, thin-section observation was used to examine the calcite vein filling within coal rock. Fractal dimension analysis was applied to quantify the complexity of calcite morphology. Numerical simulations of uniaxial compression tests on coal rock containing calcite veins of varying morphologies were conducted using a two-dimensional real failure process mesoscopic analysis software. The results revealed that the complexity of calcite morphology significantly affected the mesoscopic damage evolution characteristics of coal rock. The peak strength generally increased with the fractal dimension of the calcite veins. A positive correlation between crack rate and peak stress was observed, indicating that higher peak strengths corresponded to higher crack rates at final failure. During uniaxial compression, multiple microcracks initially appeared around the calcite vein particles, with fracture propagation directions closely aligned with the vein orientation, influencing the crack propagation direction in the coal rock. Additionally, coal rock with larger fractal dimensions exhibited more acoustic emission events, signifying more complex failure patterns. These findings contribute to a deeper understanding of how calcite vein distribution affects the mechanical properties of coal rock and provide a novel approach to studying the mesoscopic damage evolution in coal rock containing calcite veins.