深埋隧洞开挖进尺比选分析

Comparative Analysis of Deep-Buried Tunnel Excavation Footage

【目的】开挖进尺对隧洞掘进过程中围岩稳定性和施工效率具有重大影响,以西藏某深埋引水隧洞为研究对象,对其开挖进尺进行研究分析,为不同埋深下深埋隧洞开挖进尺的选取提供参考。【方法】通过FLAC3D软件对埋深300 m、550 m和800 m地质环境下的引水隧洞进行开挖进尺分别为2 m、3 m、4 m和5 m的模拟开挖,并分析围岩位移、应力分布及塑性区状况。【结果】①围岩变形随埋深的增加而增大,开挖进尺对掌子面轴向变形影响很小,侧壁位移和拱顶位移随开挖进尺的增加整体表现为匀速增大。②围岩应力集中主要出现在拱顶上方及拱底下方,开挖进尺为3~4 m时应力集中区域与开挖轮廓面距离较为合适。③围岩塑性区随埋深的增加逐步由拱顶及拱底向拱腰处扩展,最终连接成环,其深度随开挖进尺增加整体表现为匀速增大,开挖进尺为3 m时塑性区体积的增加速度显著。【结论】各埋深和开挖进尺条件下的隧洞变形、应力分布和塑性区结果表明,该工程最佳开挖进尺为3 m。

[Purposes]The excavation footage has a significant impact on the stability of the surrounding rock and construction efficiency during the tunnel excavation.Taking a deep-buried water diversion tunnel in Tibet as the research object,the excavation footage is studied and analyzed to provide reference for the selection of excavation footage for deep-buried tunnels at different burial depths.[Methods]Using FLAC3D software,the excavation of a deep-buried tunnel was simulated at 2 m,3 m,4 m and 5 m for the geological environment of 300 m,550 m and 800 m,respectively,and the surrounding rock displacement,stress distribution and plastic zone were analyzed.[Findings]①The deformation of the surrounding rock increases with the increase of burial depth,and the excavation footage has little effect on the axial deformation of the palm face,the sidewall displacement and vault displacement show an overall uniform increase with the increase of the excavation footage.②The stress concentration area of the surrounding rock mainly appears above the vault and below the arch,and the distance between the stress concentration area and the excavation profile is more suitable when the excavation footage is 3~4 m.③The plastic zone of the surrounding rock gradually expands from the top and bottom of the arch to the waist of the arch with the increase of the burial depth,and finally connects into a ring,and the depth of which increases with the excavation footage at a uniform rate,and of the volume of the plastic zone increases significantly when the excavation footage is 3 m.[Conclusions]The results of the tunnel deformation,stress and plastic zone indicate that the optimum excavation footage for this project is 3m.