层理倾角与孔道直径对页岩单轴破坏特征影响的数值研究

    NUMERICAL STUDY ON THE EFFECTS OF BEDDING INCLINATION ANGLE AND HOLE DIAMETER ON UNIAXIAL FAILURE CHARACTERISTICS OF SHALE

    • 摘要: 为探究深部地下工程中层状围岩井壁与隧道失稳破坏机理,通过构建单轴压缩条件下随机分布层理面的空心页岩数值模型,研究了层理倾角与孔道直径对含孔道页岩强度及破坏特征的影响。数值模拟结果表明:(1)含孔道页岩强度随孔径的增大逐渐减小,随层理倾角变化表现出各向异性特征且各向异性指数随孔径增加而增大,层理面与轴向力夹角影响层理面作用机理造成失稳模式的各向异性,孔道存在使受力面含缺陷造成加载中应力集中不均匀、传递路径不连续从而使页岩试样失稳强度降低;(2)在层理面与孔道共同作用下,页岩表现出各向异性的脆性破坏形式:层理0°时为沿层理与基质面的滑剪破坏,层理30°、60°时表现为沿层理面的滑移破坏,层理90°时为贯穿试样的劈裂破坏。层理倾角较小时完整页岩和含孔道页岩在破坏形式上无显著区别,层理倾角较大时含孔道页岩两侧裂纹出现差异且主裂纹随孔径增大而上移。(3)破坏时输出的声发射信号受孔径影响并随孔径增大出现不同程度的降低,通过声发射信号变化规律与时空分布特征能够评估破坏烈度并再现试样内部细观结构渐进损伤特征。研究结果有助于理解含孔道页岩失稳破坏机理,可为提升地下工程的稳定性和安全性提供理论指导。

       

      Abstract: 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 bedding plane and the axial force affects the mechanism of the bedding plane action, causing anisotropy in the destabilization 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 bedding planes and the hollow state, shale exhibits anisotropic brittle failure forms: at 0°, it undergoes shear failure along 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 difference in the failure mode between intact shale and hollow shale, but at larger angles, differences in crack appearance are observed on both sides of the hollow shale, with the main crack shifting upward with increasing pore diameter. (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 characteristics of acoustic emission signals, the severity of damage can be evaluated, and the progressive damage characteristics of the internal microstructure of the specimen can be reproduced. These findings contribute to understanding the destabilization and failure mechanism of hollow shale, providing theoretical guidance for improving the stability and safety of underground engineering.

       

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