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连拱隧道结构形式复杂,开挖与支护工序转换频繁,围岩受多次扰动,施工风险高,直接影响隧道围岩与支护结构体系的安全性。依托某浅埋偏压连拱隧道工程,采用数值分析方法评价了连拱隧道初期支护结构的安全性。结果表明,受地形偏压影响,左、右侧主洞初支结构内力和变形存在明显的不对称性,深埋侧主洞贯通而未施作二衬情况下开挖浅埋侧主洞,初支结构多个典型特征点处的安全系数均小于规范规定限值,是导致连拱隧道发生大型塌方的主要原因。浅埋偏压连拱隧道主洞开挖时应采取“先外后内”的施工工法,并保持合理的安全步距,相关结论可为相关工程提供参考。
The structure of the multi-arch tunnel is complex, the frequency of excavation and support conversion is frequent, the surrounding rock is disturbed several times, and the construction risk is high, which directly affects the safety of the surrounding rock and supporting structure of the tunnel. Relying on a shallow buried double arch tunnel project, the numerical analysis method was used to evaluate the safety of the initial arch support structure. The results show that there is obvious asymmetry in the internal forces and deformation of the primary branch structure of the left and right main tunnels due to the influence of the terrain bias. The main bore of the shallow buried side of the deep borehole, The safety factor of multiple typical feature points of the initial branch structure is less than the limit values specified in the code, which is the main reason for the large-scale landslip in the multi-arch tunnel. Shallow-buried bi-pressure multi-arch tunnel main tunnel excavation should be taken “before and after ” construction method, and maintain a reasonable safety step, the relevant conclusions can provide reference for the relevant projects.