Crack Characteristics of Carbon Fiber Reinforced Polymer Confined Coal Samples With Various Height‐to‐Diameter Ratios: A Coupled Discrete‐Continuum Numerical Investigation

Stabilizing residual pillars in room‐and‐pillar goafs is essential for ensuring the safe extraction of remaining resources and maintaining the stability of overlying load‐bearing structures. To address this challenge, an innovative reinforcement technology using carbon fiber‐reinforced polymer (CFRP) jackets was developed. Uniaxial compression tests and numerical simulation studies were conducted to evaluate its effectiveness. A coupled Particle Flow Code and Fast Lagrangian Analysis of Continua (PFC 3D ‐FLAC 3D ) numerical model was established by calibrating parameters obtained from uniaxial compression tests on CFRP‐confined coal samples with varying height‐to‐diameter ratios. The crack propagation behavior of these samples was analyzed from the perspective of microscopic progressive damage characteristics, focusing on crack initiation, propagation, and changes in characteristic stress parameters. The results demonstrated that CFRP provided effective lateral confinement, significantly enhancing the bearing capacity and stability of the coal samples. Crack evolution states at various characteristic stress points were examined, and the second‐order difference of the crack evolution curves was used to determine the ranges of crack initiation and damage stress levels for both unconfined and CFRP‐confined coal samples. Numerical simulations successfully replicated the progressive damage process and dominant failure modes of coal samples with different height‐to‐diameter ratios. These findings hold significant theoretical value for the design and maintenance of underground mining resource projects.