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针对浅埋黄土隧道在开挖过程中发生的拱顶过量沉降问题,采用颗粒离散单元法模拟了不同开挖方法和加固措施对围岩稳定和变形的影响,分析了6种工况的围岩压力分布和位移发展情况,讨论了开挖方法和加固措施对隧道围岩稳定的影响.模拟结果显示,隧道拱肩和拱脚应力集中处水平位移较大,拱部和边墙开挖为黄土隧道留核心开挖施工中的关键工序,施工中宜及早支护避免隧道发生过大变形.浅埋黄土隧道拱顶下沉量远大于周边收敛;对于相同的支护形式,留核心土下部全断面开挖法产生的位移总量约为留核心土下半断面分部开挖法的1.2倍;对于相同的开挖方法,无超前注浆支护产生的位移总量约为有超前支护的1.5倍;而有无系统锚杆的隧道围岩变形量基本相同.研究表明,浅埋黄土隧道可采取超前导管注浆减小隧道开挖变形,而系统锚杆由于支护效果不明显可考虑取消.
Aiming at the problem of excessive settlement of vault during the excavation of shallow-buried loess tunnel, the influence of different excavation methods and reinforcement measures on the stability and deformation of surrounding rock is simulated by the particle discrete element method. The surrounding rock Pressure distribution and displacement, the influence of excavation methods and reinforcement measures on the stability of tunnel surrounding rock is discussed. The simulation results show that horizontal displacement of stress concentration point of tunnel shoulder and arch foot is larger, and the arch and sidewall excavation are loess In the construction of the tunnel, the key processes in the excavation of the core should be left as early as possible to avoid excessive deformation in the construction of the tunnel. The settlement of the dome in the shallow-buried loess tunnel is far greater than that of the surrounding area. For the same support form, The total displacement produced by the section excavation method is about 1.2 times that of the excavation method with the semi-section subsoil of the remaining core in the excavation method. For the same excavation method, the total displacement caused by no-advance grouting support is about 1.5 times of that of the tunnel.The rock mass deformation of the surrounding rock with or without the system anchor is basically the same.The research shows that the shallow tunnel can take the advanced conduit grouting to reduce the tunnel excavation deformation and the system anchor is not obvious because of the support effect test Canceled.