超大埋深软岩隧道超前中导洞合理断面尺寸及应力峰值转移机制

在超大埋深软岩隧道中,通常地应力较高,且围岩软弱破碎,在施工过程中不可避免的会出现大变形现象,造成支护结构失效破坏。采用超前中导洞应力释放技术提前释放地应力,可以改善支护结构的受力状态,减小隧道变形量,保证支护结构的安全。本文依托丽香线哈巴雪山大变形隧道,采用文献调研、数值模拟及现场监测等手段对超大埋深软岩隧道超前中导洞合理断面大小进行研究,分析了中导洞不同断面大小工况下应力释放效果,最终确定中导洞合理断面大小。研究结果表明,超前中导洞断面为正洞断面面积的0.6倍时,应力释放效果较为理想,相比直接开挖正洞,采用合理超前中导洞断面时,正洞拱顶沉降及上、下台阶水平收敛值分别减小28.2%、27.64%和26.71%,且围岩中切向应力峰值向围岩深部转移了约4 m,同时,应力峰值数值有所减小,减小约5.04%。研究成果可为类似大变形隧道工程提供参考与借鉴。

Research on Reasonable Cross Section Size of Middle Pilot Tunnel in Super Deep Buried Soft Rock Tunnel

In the super deep soft rock tunnel, the crustal stress is usually high, and the surrounding rock is weak and broken. Large deformation will inevitably occur during the construction process, resulting in the failure of the support structure. Using the stress release technology of advanced pilot tunnel to release crustal stress in advance can improve the stress state of the support structure, reduce the tunnel deformation, and ensure the safety of the support structure. This article relies on the Haba Snow Mountain Large Deformation Tunnel on the Lixiang Line, and uses methods such as literature research, numerical simulation, and on-site monitoring to study the reasonable section size of the advanced middle pilot tunnel in super deep soft rock tunnels. It analyzes the stress release effect under different section sizes of the middle pilot tunnel, and ultimately determines the reasonable section size of the middle pilot tunnel. The research results indicate that the stress release effect is ideal when the cross-sectional area of the leading middle tunnel is 0.6 times that of the main tunnel. Compared with direct excavation of the main tunnel, when using a reasonable advanced middle pilot tunnel section, the settlement of the main tunnel arch crown and the horizontal convergence values of the upper and lower steps decrease by 28.2%, 27.64%, and 26.71%, respectively, and the peak tangential stress in the surrounding rock shifts about 4 meters to the deep part of the surrounding rock. Meanwhile, the peak stress value has decreased by approximately 5.04%. The research results can provide reference and inspiration for similar large deformation tunnel projects.