Mechanical response and crack evolution mechanism of sandstone with fracture infilling under non-uniform loading

LIU Gang; ZAN Yonglong; WANG Shengxuan; WANG Miao

doi:10.13247/j.cnki.jcumt.20250339

Abstract：Roadway surrounding rock is often subjected to the coupled influence of internal fracture structures and complex non-uniform loads,leading to stress redistribution,aggravated local failure,re-duced overall bearing capacity,and increased instability risk.To investigate the crack propagation and evolution characteristics of sandstone with different fracture features under non-uniform loading,three types of specimens that include intact sandstone,sandstone with prefabricated rectangular fractures,and sandstone with filled fractures were tested.A self-developed non-uniform loading apparatus was employed in combination with digital image correlation(DIC)for full-field strain monitoring,acoustic emission(AE)techniques,and FLAC3D numerical simulations to analyze crack propagation,AE re-sponse,stress field evolution,and plastic zone development.The experimental results reveal that the peak strength of sandstone is significantly controlled by fracture morphology,following the order:in-tact>filled fracture>prefabricated fracture.Based on the introduced damage factor P,the damage evolution of the three types specimens exhibits a trend of initial increase followed by a subsequent de-crease.The loading mode determines the crack propagation path,whereas fracture morphology gov-erns the failure mode:tensile failure dominates in intact specimens,tensile-shear mixed failure occurs in prefabricated fracture specimens,and shear failure prevails in filled fracture specimens.AE activity transitions from a quiescent stage to an active stage,with cumulative ringing counts increasing step-wise.A significant negative correlation exists between the b-value and cumulative ringing counts;the intact specimen maintains a relatively high b-value during the quiescent period,whereas the prefabri-cated fracture specimen exhibits the most pronounced b-value decrease at failure.Moreover,the peak frequency distribution differs markedly among specimen types.The internal stress of sandstone shows a gradient distribution positively correlated with local load intensity,with delayed peak strength across different regions.Stress gradients govern plastic zone evolution and determine crack propagation paths and coalescence behavior.This study provides theoretical insights for the support design of frac-tured rock masses and the stability evaluation of roadway surrounding rock.