Influence of CFRP jackets stiffness on the performance of coal cylinders: 3D PFC- FLAC coupled numerical investigation

Abstract

Carbon fiber reinforced polymer (CFRP) jacketed coal cylinders represent a potential new material-based method for enhancing the stability of coal pillars in goaf, and CFRP jackets stiffness is the most critical parameter. However, traditional continuum-based numerical models cannot model the meso-mechanics of coal cylinders due to its discrete nature. In this paper, a three-dimensional discrete element method (DEM) and the finite difference method (FDM) coupled numerical modeling scheme was proposed. CFRP jackets is modeled by the continuum method using FLAC^3D and the coal cylinders is modeled by the discrete element method using PFC^3D. The proposed numerical models are validated using laboratory observations. The influence of CFRP jacket stiffness on the contact force fabric, crack propagation, and characteristic stress of axially compressed coal cylinders were investigated. Numerical results demonstrate that the anisotropy of the normal contact force fabric gradually decreases with the increase in CFRP jacket stiffness. The characteristic stresses (cracking, yielding, and peak) increase significantly as CFRP jacket stiffness enhances, following a positive exponential decay function relationship. The cumulative number of cracks grows in an "S-shaped" Bidoseresp function pattern with increasing axial strain. These findings provide critical references for the application of CFRP jackets in the reinforcement of residual coal pillars in goaf areas.