隧道穿越绿泥石片岩地段施工方案优化比选

Comparison and Selection of Construction Schemes for Tunnel Crossing Chlorite Schist Section

何家寨隧道在穿越绿泥石片岩段的原设计方案采用台阶法+临时仰拱支护进行施工。项目在施工过程中按照原方案施作30m后,根据掌握的现场围岩情况及实时监控量测数据分析得出:掌子面开挖完成后,围岩的自稳能力较差,易在拱部出现坍塌、掉块等不良地质情况,需要对围岩进行及时支护,形成新的应力分布空间。初期支护完成后整个围岩沉降变形可控,满足设计要求。根据施工经验和查阅相关资料,采用环形开挖预留核心土穿越隧道绿泥石片岩段,可以最大程度减少临时支护对施工的干扰,减少临时拱架安装和拆除的工作量,降低施工成本,降低施工安全风险及难度,提高施工效率。

The original design scheme of Hejiazhai tunnel crossing chlorite segment adopts bench method and temporary inverted arch support. After 30 m construction according to the original scheme,according to the on-site surrounding rock conditions and real-time monitoring data analysis,it is concluded that after the excavation of the tunnel face,the self stability ability of the surrounding rock is poor,and it is easy to collapse,block and other adverse geological conditions in the arch,so it is necessary to support the surrounding rock in time to form a new stress distribution space. After the completion of the initial support,the settlement and deformation of the whole surrounding rock can be controlled and meet the design requirements. According to construction experience and relevant data,annular excavation is adopted to reserve core soil through the greenstone schist section of the tunnel,so as to minimize the interference of temporary support on construction,reduce the workload of temporary arch installation and removal,construction cost, construction safety risk and difficulty, and improve the construction efficiency.