Failure and energy evolution of CFRP-confined coal samples under cyclic loading and unloading

LIU Honglin; GONG Xiaohan; ZHAO Hongchao; HUANG Haishan; SHI Guangfeng; TIAN Jiajie

doi:10.13225/j.cnki.jccs.2025.0335

Abstract：Carbon fiber reinforced polymer(CFRP)demonstrates promising application prospects in reinforcing protect-ive coal pillars due to its lightweight,high-strength,and corrosion-resistant.To further investigate the mechanical re-sponse mechanism of CFRP-confined coal pillars under the dynamic evolution of mining-induced stress fields,particu-larly under cyclic loading and unloading,both the failure characteristics and energy evolution laws of CFRP-confined coal specimens under cyclic loading and unloading were systematically investigated in the present research.Upon the principle of energy dissipation and employed the acoustic emission RA-AF analysis method.The results indicate that:① Compared to conventional uniaxial compression,the strengths of coal specimens confined with 0,1,and 3-layer CFRP under cyclic loading and unloading increased by 2.65％,10.17％,and 1.22％,respectively.The envelope curve of their stress-strain curves exhibited similarity to the stress-strain curve under uniaxial loading.② The coal specimens exhibited significant deformation memory characteristics under cyclic loading and unloading.The area and reversal amplitude of the hysteresis loops formed by their stress-strain curves were positively correlated with the number of loading-unloading cycles,while the loop density was negatively correlated with the number of cycles.③ Both the total accumulated energy and the elastic strain energy density of the coal specimens increased with rising axial stress,exhibiting an exponential functional relation-ship with axial stress in magnitude.④ As the number of CFRP layers increased from 0 to 3,the dissipation energy density shifted from a U-shaped distribution to a J-shaped distribution,and the dissipation energy rate changed from an L-shaped distribution to a V-shaped distribution.The proportions of dissipation energy were 6.62％,31.46％,and 42.56％,respect-ively,showing a trend of initially rapid increase followed by a slower increase.⑤ Under cyclic loading and unloading,the proportion of tensile failure in coal specimens varied significantly under different confinement conditions.This experi-mental study reveals the deformation,failure,and energy evolution characteristics of CFRP-confined coal specimens un-der cyclic loading and unloading,providing theoretical support for further promoting the industrial application of CFRP in coal pillar reinforcement.