The distribution of stress and the normal extrusion load threshold in weak interlayer are crucial for direct shear test of filled rock joints, but there is a lack of theoretical research in this area. First, an analytical solution for stress distribution was derived using a semi-inverse method. Then, it is compared by the numerical simulation method. Finally, the influence of the width and thickness of weak interlayer on the extreme values of stress components was analyzed, and the distribution pattern of the normal extrusion load was discussed. The results show that under the same conditions, the analytical solution and the numerical simulation results are in good agreement. The maximum horizontal stress in the weak interlayer decreases with increasing width and increases with increasing thickness, while the change of the minimum is opposite. The normal extrusion load increases first and then decreases along the width direction of the weak interlayer. By comparing the normal extrusion load with the empirical value, the mechanism of extrusion failure in the weak interlayer is revealed.

中文翻译：

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压缩充填岩节理应力分布及挤压载荷阈值研究

软弱夹层的应力分布和法向挤压载荷阈值对于充填岩石节理直剪试验至关重要，但目前这方面的理论研究还很缺乏。首先，使用半逆方法导出应力分布的解析解。然后通过数值模拟的方法进行比较。最后，分析了软弱夹层的宽度和厚度对应力分量极值的影响，并讨论了法向挤压载荷的分布规律。结果表明，在相同条件下，解析解与数值模拟结果吻合较好。软弱夹层最大水平应力随着宽度的增加而减小，随着厚度的增加而增加，而最小值的变化则相反。法向挤压载荷沿弱夹层宽度方向先增大后减小。通过将正常挤压载荷与经验值进行比较，揭示了薄弱夹层挤压失效的机理。