Filled rock discontinuities are commonly encountered in underground engineering excavations, and their mechanical behavior has a significant impact on the stability of surrounding rocks. However, their performance under three-dimensional stress conditions has rarely been explored in the past. In this study, we summarized the typical failure characteristics of filled structural planes in deep-buried tunnels and conducted laboratory true triaxial tests on granite specimens to investigate the effect of dip angle and infill thickness on the failure characteristics of high-stress brittle surrounding rocks. The study monitored the characteristics of vertical stress-displacement, acoustic emission, acceleration, and failure process of granite specimens during the loading process and revealed the failure mechanism of brittle rock masses under the influence of infill thickness and structural plane dip angle. The results showed that the dip angle of structural planes has a significant influence on the failure mode of rock masses in deep tunnels. There exists a critical range of dip angles, within which the rock mass undergoes shear slip failure along the pre-existing structural plane, manifested by rock spalling near the structural plane. Beyond this critical range, the rock mass experiences strain-type brittle failure, characterized by violent rock ejection. Furthermore, the filling of structural planes can change the failure mode of rock masses and lead to more severe damage when the friction coefficient of the structural plane falls below a specific threshold. Additionally, it was revealed that a perpendicular ejection force exists on the free surface of the rock mass under loading, which is approximately vertical to the normal direction and is the primary factor responsible for the formation of vertical parallel cracks within the rock mass. The findings of this work are of paramount importance for comprehending the failure characteristics of deep-buried tunnels containing infilling joints.

中文翻译：

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深埋隧道中的脆性岩体破坏：不同倾角的填充结构面的作用

充填岩结构面是地下工程开挖过程中经常遇到的问题，其力学行为对围岩的稳定性有显着影响。然而，过去很少探讨它们在三维应力条件下的性能。本研究总结了深埋隧道充填结构面的典型破坏特征，并对花岗岩试件进行了室内真三轴试验，研究了倾角和充填厚度对高应力脆性围岩破坏特征的影响。研究监测了花岗岩试件在加载过程中的竖向应力位移、声发射、加速度和破坏过程特征，揭示了填充厚度和结构面倾角影响下脆性岩体的破坏机理。研究结果表明，结构面倾角对深埋隧道岩体破坏模式有显着影响。存在一个临界倾角范围，在该倾角范围内，岩体沿原有结构面发生剪切滑移破坏，表现为结构面附近的岩石剥落。超过这个临界范围，岩体会经历应变型脆性破坏，其特征是剧烈的岩石喷射。此外，当结构面的摩擦系数低于特定阈值时，结构面的填充可以改变岩体的破坏模式并导致更严重的破坏。此外，研究还发现，在荷载作用下，岩体自由表面上存在一个近似垂直于法线方向的垂直弹射力，是岩体内部形成垂直平行裂缝的主要因素。这项工作的结果对于理解含有填充缝的深埋隧道的破坏特征至关重要。