When the axial orientation of a pillar aligns at a specific angle relative to the direction of maximum principal stress,it invariably experiences a combination of compressive and shear forces,markedly altering its mechanical behavior in contrast to a pillar subjected solely to compression.This in-vestigation employs an enhanced compression-shear combined loading apparatus to scrutinize the creep mechanical properties of coal rock under simultaneous compressive and shear stresses.Employing acoustic emission technology,this research delineates the evolution of micro-cracks and characterizes the acoustic emission energy profiles in coal rock,elucidating the damage mechanisms influencing its me-chanical properties across varying loading angles.Results indicate that with an increasing loading angle,there is a general decline in the peak strength,overall duration of creep tests,creep failure stress,and long-term strength of coal rock;however,the ratio of creep failure stress and long-term strength to peak strength exhibits minimal alteration with the angle.The fracture pattern of coal rock transitions from ten-sile failure at θ=0° to shear failure at θ=5°,10° and 15°.The cumulative acoustic emission energy dem-onstrates a strong correlation with the long-term strength of the structure;a diminution in long-term strength correlates with reduced cumulative acoustic emission energy,suggesting that the shear stress component facilitates crack propagation with less energy absorption.The onset and proliferation of inter-nal micro-cracks in coal rock,coupled with the diminished frictional resistance among mineral particles,constitute critical determinants of sample failure.The findings furnish a substantial theoretical foundation for the evaluation of long-term stability in shear-affected pillars.
维普
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