隐式中墙连拱隧道修建优化设计

Optimized Design for the Construction of a Double-Arch Tunnel with a Concealed Mid-Partition

隐式中墙复合式连拱隧道在长距离浅埋暗挖施工过程中,面临管棚超前支护施作工序复杂、先开挖侧隧道拱腰至边墙处应力集中以及中墙顶部区域夹岩稳定性差等技术难题。文章以某一具体工程为例,为解决大管棚工作室对连拱隧道施工效率的影响问题,采用了无室管棚技术;并从中墙顶部区域设置加长网状的非等参系统锚杆、中墙与先行洞衔接处初期支护的圆顺过渡和临时中墙两侧设置自进式锚杆悬吊这三个方面对隐式中墙复合式连拱隧道进行了优化设计和计算分析。分析结果表明:在采用上述三种结构优化设计后,隐式中墙复合式连拱隧道的施工安全性得到大幅提高;隐式中墙复合式连拱隧道采用优化结构,并采用无室管棚技术,实现了连拱隧道的安全快捷施工,具有较好的应用前景。

During the construction of a long and shallow double-arch tunnel with a concealed mid-partition, some technical difficulties are encountered, such as the complicated construction procedure of pipe-roof advance support, stress concentrations at both the haunch and side wall while excavating the pilot tunnel and poor stability of sand- wiched rock on top of the mid-partition, etc. Using a specific project as an example, pipe-roof technology without a chamber was adopted to decrease the influence on construction efficiency of the double-arch tunnel. The optimized design and calculation analysis of a double-arch tunnel with a concealed mid-partition was carried out with the three aspects of installing long, meshy non-isoparametric system bolts at the top of mid-partition; utilizing a smooth transition between the mid-partition and preliminary lining of the pilot tunnel; and installing suspended self-drill- ing rock bolts on both sides of the temporary mid-partition. Analysis results show that the construction safety of a double-arch tunnel with a concealed mid-partition is greatly improved by the above-mentioned optimizations; for a double-arch tunnel with a concealed mid-partition, using optimized structures and pipe-roof technology without a chamber enables rapid and safe construction, indicating a positive prospect for engineering application.