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大风垭口隧道跨越了哀牢山大断裂带并两次穿越南溪河,洞内岩性十分复杂,地下水极为丰富,施工难度极大。施工过程中,下行线进口K 255+276~+288段发生了一次特大涌水和土石流,致使有长176 m的隧道被淹埋,并在隧道正上方形成一个连通至180 m高的巨大陷坑。对此,专门采用了地震CT和高密度电法做了全面的地质调查,进行了综合治理设计,并采取两端封堵预注浆固结、环状留核心土13步法开挖、先拱后墙法衬砌、8~20 m径向自进式锚杆与小导管深孔注浆加固及综合防排水等施工技术,顺利地渡过了涌水、坍方段,整体施工质量良好。
The Dafu Pass Tunnel spans the Ailao Mountain large fault zone and traverses the Nanxi River twice. The lithology in the cave is very complicated and the groundwater is extremely rich. The construction is extremely difficult. During the construction, a gigantic water inflow and earth-rock flow occurred in the downward line K 255 + 276 ~ + 288. As a result, a tunnel with a length of 176 m was submerged and a huge crater connecting to a height of 180 m was formed just above the tunnel. In this regard, specifically the use of seismic CT and high-density electric method to do a comprehensive geological survey conducted a comprehensive management of design, and to take both ends of the plugging pre-grouting consolidation, retaining the ring retaining 13-step excavation of the core soil, the first Arch back wall lining, 8 ~ 20 m radial self-propelled anchor and small conduit deep hole grouting reinforcement and integrated drainage and other construction techniques, smoothly through the gushing water, collapse section, the overall construction of good quality.