NUMERICAL STUDY ON THE EFFECTS OF BEDDING INCLINATION AN-GLE AND HOLE DIAMETER ON UNIAXIAL FAILURE CHARACTERIS-TICS OF SHALE
To investigate the destabilization and failure mechanism of layered surrounding rock and tunnel walls in deep underground engineering,a numerical model of hollow shale with randomly distributed bedding planes under uniaxial compression conditions was constructed.The influence of bedding angle and pore diameter on the strength and failure characteristics of hollow shale was studied.The numerical simulation results indicate that:(1)The strength of hollow shale gradually decreases with increasing pore diameter and shows anisotropic characteristics with changes in bedding angle.The anisotropy index increases with increasing pore diameter.The angle between the bed-ding plane and the axial force affects the mechanism of the bedding plane action,causing anisotropy in the destabi-lization mode.The hollow state leads to uneven stress concentration on defective surfaces and discontinuous stress transfer paths,thereby reducing the instability strength of shale specimens.(2)Under the combined action of bed-ding planes and the hollow state,shale exhibits anisotropic brittle failure forms:at 0°,it undergoes shear failure a-long the bedding and matrix planes;at 30° and 60°,it exhibits sliding failure along the bedding planes;at 90°,it undergoes splitting failure penetrating the specimen.When the bedding angle is small,there is no significant differ-ence in the failure mode between intact shale and hollow shale,but at larger angles,differences in crack appear-ance are observed on both sides of the hollow shale,with the main crack shifting upward with increasing pore diam-eter.(3)The acoustic emission signals emitted during failure are influenced by the pore diameter and show varying degrees of attenuation with increasing diameter.By analyzing the variation law and spatiotemporal distribution char-acteristics of acoustic emission signals,the severity of damage can be evaluated,and the progressive damage char-acteristics of the internal microstructure of the specimen can be reproduced.These findings contribute to under-standing the destabilization and failure mechanism of hollow shale,providing theoretical guidance for improving the stability and safety of underground engineering.
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