黔张常铁路高山隧道巨型溶洞处理技术研究

黔张常铁路高山隧道高位斜穿巨型溶洞，巨型溶洞体量大，整体稳定性较差，洞壁危岩分布较多，危岩向洞内位移，落石危险时有发生。为解决巨型溶洞处理带来的困难，降低安全风险，针对巨型溶洞提出线路绕避、回填处理和桥跨处理3类11个处理方案，在综合考虑施工、运营安全及经济性的基础上，选择回填处理方案，并最终确定“回填洞砟+上部注浆加固”的处理方案。施工中形成溶洞分阶段回填、洞壁洞顶锚网喷安全防护、回填体注浆加固、隧道明洞结构保护性施工和回填体工后沉降预处理等一系列关键施工技术。超厚回填体在线沉降监控和施工过程控制结果表明，溶洞处理施工顺利、处治方案技术可靠、成本经济，可为类似工程提供借鉴。

Treatment Technology of Giant Karst Cave of Gaoshan Tunnel on  Qianjiang Zhangjiajie Changde Railway

The Gaoshan Tunnel on Qianjiang Zhangjiajie Changde Railway obliquely passes through a giant karst cave at high level. The karst cave has super large size, poor overall stability, and many dangerous rocks distributed on the cave wall. Rock fallings caused by the displacement of dangerous rocks occur from time to time, which makes the treatment of the cave very difficult. Hence, 3 kinds of treatment schemes, i.e. line avoidance, backfill treatment and bridge span treatment, are put forward. Considering the factors such as construction, operation safety and economy, backfill treatment is selected, and the scheme of "backfill cave ballast + upper grouting reinforcement" is finally determined. During the construction, a series of key construction technologies, i.e. backfilling by stages, safety protection of bolt mesh spraying on the wall and roof of the cave, grouting reinforcement of backfills, protective construction of the structure of the tunnel and settlement pretreatment after construction of backfills, has been formed. The on line settlement monitoring and construction process control of the super thick backfills show that the process of cave treatment is smooth, the treatment technologies are feasible, and the cost is rational. The results can provide reference for similar project in the future.