Axial compressive behavior of partial CFRP-jacketed coal samples: Effects of CFRP layers and strip coverage ratio

Abstract

Carbon fiber-reinforced polymer (CFRP) confined coal samples significantly improve the axial compressive behavior and stability of the internal core coal, demonstrating promising applications for stabilizing abandoned coal pillar in goaf. However, current research has predominantly focused on uniform confinement, with limited attention given to partial confinement. Moreover, the effectiveness of partial strengthening is highly dependent on the number of CFRP layers and the strip coverage ratio of the CFRP jacket. To address this, thirty-nine partial CFRP-jacketed coal samples were designed, and axial compressive behavior tests were conducted on samples with varying CFRP layers. The results revealed that the post-peak stress-strain curves exhibited an extended plateau stage, alongside a notable increase in the ductility coefficient, indicating that partial CFRP confinement effectively enhances the post-peak behavior of coal samples. For a constant number of CFRP layers, the peak strength and its enhancement ratio initially increased, then decreased, and subsequently increased again with the rising strip coverage ratio. The strip coverage ratio was found to have a more significant influence on peak strength than the number of CFRP layers. Furthermore, at a constant number of CFRP layers, the hoop peak strain at different positions within the coal samples increased as the strip coverage ratio rose. A modified strength model for partial CFRP-jacketed coal samples was developed, and its validation through the integral absolute error index demonstrated strong performance and high precision.