Constraint Mechanism and Mechanical Characteristics of CFRP Partially Wrapped Coal Columns

Carbon fiber-reinforced plastic (CFRP) wrapping is a promising technique for enhancing the structural integrity of coal columns. When applied to coal columns in roadway environments, CFRP reinforcement offers significant advantages over unreinforced columns. Specifically, the compressive strength of coal columns subjected to triaxial compression is markedly higher than that of columns subjected to uniaxial compression, primarily due to the restricted lateral expansion in the former case. This study investigates coal column specimens with varying CFRP layer configurations and net spacing ratios, evaluating mechanical properties such as stress-strain behavior, peak strength, and ultimate strain through uniaxial compression testing. The research explores the impact of CFRP confinement on the mechanical performance and damage modes of coal columns under different conditions. The results indicate that coal columns confined by CFRP strips or fully wrapped with CFRP exhibit similar mechanical behaviors. CFRP strip confinement provides a notable strengthening effect under uniaxial compression, with peak strength and deformation resistant capacity significantly improved as the net spacing ratio decreases and the number of CFRP layers increases. Additionally, the CFRP reinforcement effectively mitigates lateral expansion, alters the failure mode, and delays the onset of damage. Furthermore, using the Richart and Hoek-Brown models, the study incorporates the test data for model refinement and comparative analysis, leading to the development of a modified Richart strength model for CFRP-constrained coal columns.