大断面黄土隧道初期支护变形控制技术研究

Research on Control Technology of Initial Support Deformation of Large Section Loess Tunnel

大断面黄土隧道围岩应力较大段落开挖后极易发生较大变形,特别是在含水率大、围岩软弱的情况下。若围岩暴露时间过长、初期支护刚度不足或岩体渗水软化,易造成坍塌事故。为有效解决围岩应力较大段落初期支护开裂掉块、钢架扭曲等技术难题,结合蒙华铁路麻科义隧道施工,通过比较传统的三台阶大拱脚临时仰拱法和设置围岩应力释放装置两种方法,进行初期支护变形控制现场试验研究。结果表明,两种方法均能有效控制初期支护变形开裂,但设置围岩应力释放装置能更加充分发挥围岩的自承能力,实现工法的简化,具有成本低、机械化程度高、施工进度快、劳动强度小、可有效防止后期拱墙衬砌开裂等优点。

Large-section loess tunnels with large surrounding rock stresses are prone to large deformations after excavation,especially in the case of large water content and weak surrounding rocks.If the surrounding rock is exposed for too long,the initial support stiffness is insufficient,or the rock mass seeps through and softens,collapse accidents are likely to occur.In order to effectively solve the problems such as initial support cracks and breaks,and steel frame distortion in the section with large surrounding rock stress,we compared two methods of traditional three-step large arch foot temporary arching and installing the stress relief devices in surrounding rocks in combination with the construction of Makeyi Tunnel of Menghua Railway,and carried out field test research on initial support deformation control.The results show that both methods can effectively control the initial support deformation and cracking,but the surrounding rock stress relief device can give full play to the surrounding rock's self-supporting ability and simplifies the construction method.Beyond that,it has the advantages of low cost,high degree of mechanization,fast construction schedule,low labor intensity,and effectively preventing the cracking of the arch wall lining at the later stage.