考虑软弱夹层厚度的岩体力学响应及破坏特征研究

作为一种典型的地质结构，软弱夹层与硬脆性岩体共同形成了围岩层状复合结构，进而显著影响着隧洞围岩的稳定。以往对含软弱夹层的复合岩石的研究多集中于单轴、双轴或常规三轴，对隧洞临空面处真三轴应力路径下的复合围岩力学性质和破坏特征缺乏分析讨论。通过制作的含不同厚度的软弱夹层复合岩样，探讨了软弱夹层厚度对隧洞临空面围岩力学响应和破坏特征的影响。研究表明：软弱夹层厚度显著影响着复合岩样峰值应力和应变，随着厚度的增大，软弱夹层上方岩块向临空面方向的滑移变形逐渐增大，软弱夹层压缩变形逐渐减小；复合岩样靠近临空面的岩石单元破坏模式随着软弱夹层厚度的增大逐渐由拉剪混合破坏转变为张拉破坏，且宏观裂隙数量和破坏范围均逐渐减小，而远离临空面的岩石单元则由剪切破坏逐渐转变为基本无损伤断裂；不同厚度的隧洞侧帮复合围岩的破坏区域均集中在软弱夹层及其上方围岩处，软弱夹层下方围岩则基本保持稳定；在应力分布方面，软弱夹层厚度越大，最大压应力越向深部软弱夹层处转移，而拉应力区分布范围越小，但拉应力区深度越大。

Mechanical response and failure characteristics of rock mass considering the thickness of weak interlayer

As a typical geological structure, the layered composite structure of surrounding rock is formed by weak interlayer and hard brittle rock, and it significantly affects the stability of tunnel surrounding rock. In the past, the research on composite rock with weak interlayer focused on uniaxial, biaxial or conventional triaxial stress paths, and the mechanical properties and failure characteristics of composite rock at the free face of tunnel under true triaxial stress path were lack of analysis and discussion. In this study, the influence of the thickness of weak interlayer on the mechanical response and failure characteristics of surrounding rock at the free face is discussed based on the composite rock samples with different thicknesses of weak interlayer. The results show that: (1) The thickness of weak interlayer significantly affects the peak stress and strain of composite rock samples. With the increase of thickness, the sliding deformation of rock blocks above the weak interlayer gradually increases, and the compression deformation of the weak interlayer decreases gradually. (2) With the increase of thickness of the weak interlayer, the failure mode of the rock element near the free face of the composite rock sample gradually changes from mixed tension shear failure to tension failure, and the number and failure range of macro cracks gradually decrease, while the rock element far away from the free face gradually changes from shear failure to basically undamaged fracture. (3) The failure areas of composite surrounding rock of side wall with different thicknesses are concentrated on the weak interlayer and the surrounding rock above it, while the surrounding rock below the weak interlayer is basically stable. In terms of stress distribution, with the increase of thickness of the weak interlayer, the maximum compressive stress gradually transfers to the deep weak interlayer, and the tensile stress area gradually decreases, while the depth of the tensile stress area gradually increases.