A weak interlayer zone (WIZ) is a poor zonal geotechnical system with loose structure, weak mechanical properties, variable thickness, random distribution, and strong extension, that occurs between different rock strata (e.g., tuff and basalt), due to the intense tectonic movement, representing a potential threat to the overall stability of rock masses with WIZs in large underground cavern excavations. Focusing on the excavation-induced hazards in the weak interlayer zone (WIZ) occurring in underground cavern under high geostress, the mechanical response of WIZ under different loading and unloading stress paths has been well investigated and unearthed, by a series of automatic stress path controlled triaxial tests, as well as through scanning electron microscope (SEM) analysis. Results show that the mechanical characteristics of WIZ are closely related to the initial confining pressure and stress paths. Sudden increases in the circumferential strain and strong dilations of WIZ occur from the start of unloading, among which the unloading total strains are most strongly promoted by stress path II (i.e., axial pressure loading and confining pressure unloading), whereas the unloading stress path IV (i.e., axial pressure and confining pressure unloading) has the greatest promotion on enhancing the plastic volumetric dilatation. The deformation modulus and the Poisson’s ratio follow a deterioration law under the unloading process of confining pressure, and it is the unloading stress path II that most influences the damage of elastic parameters. The ultimate bearing strength, the internal friction angle, and the cohesion of WIZ appear extremely obvious degradation in course of unloading, among which the damage effect of stress path IV is the most remarkable. The macroscopic and mesoscopic analyses reveal that the failure mechanism of WIZ under complicated unloading stress paths lays in the accumulation and propagation of axial and circumferential cracks and fractures, as well as pervasive particle breakage, with the intergranular fractures, transcrystalline fractures, and the shear scratches on a meso level. The research could provide an effective basis and good lessons for the mechanical response and failure mechanism of WIZ under unloading stress paths in underground cavern under high geostress.

中文翻译：

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高地应力下地下洞室弱夹层机械响应开挖应力路径的洞察

弱夹层带（WIZ）是由于强烈的构造作用，发生在不同岩层（如凝灰岩和玄武岩）之间的一种结构松散、力学性能弱、厚度可变、分布随机、伸展性强的带状岩土系统。运动，这对大型地下洞穴开挖中具有 WIZ 的岩体的整体稳定性构成潜在威胁。针对高地应力下地下洞室弱夹层带（WIZ）的开挖致危害，通过一系列自动应力路径控制，对WIZ在不同加载卸载应力路径下的力学响应进行了很好的研究和挖掘。三轴测试，以及通过扫描电子显微镜 (SEM) 分析。结果表明，WIZ 的力学特性与初始围压和应力路径密切相关。WIZ的周向应变突然增加，从卸载开始就发生强烈膨胀，其中卸载总应变受到应力路径II（即轴向压力加载和围压卸载）的强烈推动，而卸载应力路径IV （即轴向压力和围压卸载）对增强塑性体积膨胀的促进作用最大。变形模量和泊松比在围压卸荷过程中遵循劣化规律，卸荷应力路径Ⅱ对弹性参数的破坏影响最大。极限承载强度、内摩擦角、WIZ的内聚力在卸载过程中出现极其明显的退化，其中应力路径IV的破坏效果最为显着。宏观和细观分析表明，复杂卸载应力路径下WIZ的破坏机制在于轴向和周向裂纹和裂缝的积累和扩展，以及普遍的颗粒破碎，以及晶间断裂、穿晶断裂和剪切划痕。在中观层面。该研究可为高地应力下地下洞室卸载应力路径下WIZ的力学响应及破坏机理提供有效依据和借鉴。宏观和细观分析表明，复杂卸载应力路径下WIZ的破坏机制在于轴向和周向裂纹和断裂的积累和扩展，以及普遍的颗粒破碎，以及沿晶断裂、穿晶断裂和剪切划痕。在中观层面。该研究可为高地应力下地下洞室卸载应力路径下WIZ的力学响应及破坏机理提供有效依据和借鉴。宏观和细观分析表明，复杂卸载应力路径下WIZ的破坏机制在于轴向和周向裂纹和断裂的积累和扩展，以及普遍的颗粒破碎，以及沿晶断裂、穿晶断裂和剪切划痕。在中观层面。该研究可为高地应力下地下洞室卸载应力路径下WIZ的力学响应及破坏机理提供有效依据和借鉴。并且剪切在中观水平上划伤。该研究可为高地应力下地下洞室卸载应力路径下WIZ的力学响应及破坏机理提供有效依据和借鉴。并且剪切在中观水平上划伤。该研究可为高地应力下地下洞室卸载应力路径下WIZ的力学响应及破坏机理提供有效依据和借鉴。