Numerical Simulation Study on the Creep Behavior and Reinforcement Mechanisms of Carbon Fiber Reinforced Polymer Confined Coal Pillars

ABSTRACT The long‐term stability of remnant coal pillars is paramount for ensuring safety in mining operations. Although carbon fiber reinforced polymer (CFRP) reinforcement can significantly enhance the short‐term load‐bearing capacity of coal pillars, its long‐term durability has not been sufficiently investigated. This study, based on the Burgers‐parallel bonded hybrid contact model, developed a coupled Discrete Element Method‐Finite Difference Method (DEM‐FDM) numerical approach to simulate graded loading creep behavior of coal pillars with multiple CFRP layers. The effects of CFRP layers on macro‐meso creep behavior were systematically analyzed. The effects of the number of CFRP layers on macroscopic and mesoscopic creep behavior were systematically analyzed. The results indicate that both creep strength and creep strain increase nonlinearly with the number of layers and gradually approach saturation, following a negative exponential decay model. The steady‐state creep rate progressively rises before instability and exhibits an exponential surge during the failure stage. Acoustic emission activity intensifies with increasing CFRP layers and stress levels, showing exponential growth characteristics during instability. The decelerating, steady‐state, and accelerating creep stages correspond to crack initiation, stable propagation, and concentrated release, respectively. The failure mode shifts from end‐shear failure in unconfined specimens to mid‐span tensile failure under CFRP confinement. The range of strong contact forces decreases with more CFRP layers, also following a negative exponential decay. Considering cost‐benefit analysis and structural safety reserves, three CFRP layers are identified as the optimal configuration. This study provides valuable references for engineering reinforcement design and rockburst prevention.