To elucidate the impact of porosity on the mechanical properties and deformation failure characteristics of coal samples,numerical simulations of uniaxial compression on coal samples of varied porosities were con-ducted using UDEC-Trigon.The mechanical properties and deformation failure characteristics of coal samples with different porosities were investigated,exploring the impact of porosity on macroscopic deformation failure,microscopic crack development and acoustic emission evolution.The results show that increasing porosity result in an exponential decrease in the uniaxial compressive strength(UCS)and residual strength of coal samples.The elastic modulus and deformation modulus gradually decreased,while Poisson's ratio showed a gradual in-crease.Under the influence of porosity,internal microscopic tensile cracks in coal samples were more prone to initiation,expansion and coalescence.With the increase of porosity,the instability of coal samples transitioned from tensile-shear brittle failure to tensile ductile failure,facilitating the formation of macroscopic cracks and sig-nificantly increasing their quantity and distribution range.Porosity-induced changes shifted the acoustic emission signals of coal sample from sudden and rapid evolution to a slower evolution.Tensile stress at the tip of pores drove the initiation and extension of microscopic tensile cracks.Higher porosity led to a broader distribution range and increased magnitude of tensile stress,resulting in numerous microscopic cracks initiation,propagation,and coalescence and leading to a larger extent of coal sample failure and an increased number of macroscopic cracks.The distribution and evolution of tensile stress within coal samples were significantly influenced by the characteristics of pore structure,which influencing the initiation,extension,and coalescence of microscopic cracks at pore tips.This research provides guidance for mine roadway drilling pressure relief to prevent rock bursts.
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