对隧道TBM导洞扩挖法施工的探讨与展望

介绍导洞法的概念及其作用,分析导洞法的特点及其适用条件。以2座已建成运营的单洞双线铁路隧道和1座施工图设计阶段的双洞6车道高速公路隧道共3座地质差异较大的特长隧道为依托,主要进行以工期关键工序--挖掘和初期支护为研究对象的工期方案模拟,并比对模拟方案工期与实际或施工图设计工期。认为： 1）软弱破碎围岩比例高的单洞隧道应慎重采取TBM导洞法。2）仅用1台TBM单向导洞法取代工期性辅助导坑对单洞特长隧道而言是不可行的;在单洞特长隧道建设中,2台TBM相向实施TBM导洞法是可行的,但须具备设置辅助导坑的条件,辅助导坑宜按无轨双车道断面设置。3）在双洞特长隧道建设中,双洞各用1台TBM相向平行导洞法则有望取代工期性辅助导坑;双洞特长隧道实施TBM导洞法,在工期、成本(投资)、不良地质应对方面有明显优势。4）川渝地区广泛分布的泥岩、砂岩、砂质泥岩、泥质砂岩及其互层地层具有实施TBM导洞法的天然地质优势。最后对TBM导洞法的应用前景进行了展望。

Discussion and Prospects on TBM Pilot-heading and Enlarging Method

In this paper, the concept and effect of pilot heading method are presented, and the characteristics and applicable conditions of pilot heading method are analyzed. The construction schedules of 3 tunnels located in different geological conditions are simulated in terms of excavation and primary support, and comparison and contrast is made between simulated construction schedules and actual/designed construction schedules. Conclusions drawn are as follows: 1) TBM pilot heading method is not suitable for single tube tunnels located in soft, weak and fractured strata; 2) Instead of other construction galleries, TBM pilot heading method may be adopted for single tube tunnels. 3) Twin TBM pilot heading method is suitable for twin tube extra long tunnels, which has advantages in terms of construction schedule, cost and coping with unfavorable geological conditions; 4) TBM pilot heading method is suitable for the construction of tunnels in Sichuan and Chongqing area. Finally, the application of TBM pilot heading method is prospected.