隧道拱脚塌方施工加固及监测分析

 山岭隧道施工过程中经常会遇到隧洞塌方等事故，而拱脚塌方又具有破坏性大、隐蔽性强等特点，常在实际工程中被忽视。结合永宁高速高宝隧道施工过程中发生的拱脚塌方事故，分析隧道拱脚塌方的原因及所采用的加固措施；对拱脚塌方段周边断面及加固后塌方段断面的围岩位移和支护结构应力进行监测，确保围岩稳定及施工安全。结果表明：拱脚塌方加固处理方案实施可行，加固段围岩变形及应力均得到较好的控制，塌方段的小导管注浆加固效果较好；砂土状围岩的隧洞施工过程中应注意地下水位及降雨引起围岩吸水膨胀导致的拱脚塌方；发生拱脚塌方时应尽快封闭塌方围岩，对塌方段附近一定范围内的隧洞进行加固，并做好排水措施；对塌方段周边进行监测，待监测结果稳定后对塌方段采用单侧壁导坑开挖法进行短挖短衬施工。研究结论可为类似条件下工程的设计、施工和监测提供借鉴意义。

REINFORCEMENT CONSTRUCTION AND MONITORING ANALYSIS OF ARCH SPRINGING COLLAPSE OF TUNNEL

Construction process of mountain tunnel often encounters tunnel collapse，and collapse of arch springing has characteristics of large destructiveness and difficult detection，which is often neglected in actual project. In the Gaobao tunnel of Yongning express way，arch springing collapsed during construction. The cause of arch springing collapse and its reinforcement measure are studied. The displacement and stress of tunnel section near collapsed zone and collapsed zone after reinforcement are monitored to make sure that the surrounding rock is stable and the construction process is safe. The results show that：consolidation measure of arch springing is practicable，surrounding rock deformation and stress are well controlled，ductile injecting method is good. In the construction of tunnel making up of sand soil，much attention should be paid to the accidents caused by expansion of surrounding rock induced by rising up of ground water and rainfall infiltration. When accident of arch spring collapse occurs，surrounding rock of collapsed zone should be sealed up as quickly as possible，and surrounding rock within limits near collapsed zone should be reinforced. Excavation method of one side-surrounding pilot tunnel with short-line short-dig should be applied after monitoring result being stable near collapsed zone. The experience and conclusions presented can provide reference to design，construction and monitoring research of similar tunnels.