不良地质段隧洞支洞进主洞三岔口施工技术

Construction Technology for Fork Road of Tunnel Branch into Main Tunnel in Unfavorable Geological Section

考虑施工进度及施工期间洞内排水,滇中引水工程昆明段施工Ⅰ标松林隧洞于主洞桩号SLT0+723.675处设施工支洞,1号施工支洞为不良地质段平支洞进主洞修建,支洞进主洞三岔口为施工关键,隧洞支洞进主洞三岔口跨度大,围岩软弱、自稳能力差,施工中反复挑顶扩挖,工序转换复杂,对围岩扰动大,应力急剧变化,极易产生掉块、坍塌事故,现场合理安排施工计划,施工中遵循“弱爆破、少扰动、短开挖、强支护”的原则施工,保证了三岔口洞室结构的整体稳定,有效避免了安全事故的发生,同时确保了工程进度。

Considering the construction progress and drainage in the tunnel during construction, Songlin Tunnel in Bid Ⅰ of Kunming Section of Yunnan Water Diversion Project sets up a construction branch at main tunnel stake No.SLT0+723.675.No.1 construction branch tunnel is built for entering the main tunnel of flat branch tunnel in unfavorable geological section, and three forks of branch tunnel entering the main tunnel are key construction points.The span of the three forks entering the main tunnel of the tunnel branch is large, and the surrounding rock is weak and its self-stability is poor.Repeated roof picking and expansion during construction, complex process conversion, large disturbance to surrounding rocks, rapid stress changes, are very prone to block fall and collapse accidents.Reasonable construction plan is arranged on site and the principle of "weak blasting, less disturbance, short excavation and strong support" is followed during construction, which ensures the overall stability of the chamber structure at the three forks, effectively avoids the occurrence of safety accidents and ensures the progress of the project.