挤压性围岩小间距隧道结构受力特性分析

Analysis of Mechanical Behaviors of the Small-spacing Tunnel in Squeezing Rock Masses

小间距隧道的工程难点主要是群洞效应以及中间岩柱的稳定性,尤其是在挤压性围岩环境中,施工中出现先挖先裂、左挖右裂的现象是十分棘手的难题。文章依托新城子隧道出口喇叭口段挤压性围岩典型大变形案例,提出了超前导洞应力释放工法,并通过结构测试及数值对比分析,验证超前导洞应力释放工法的效果。结构受力测试结果及数值对比分析显示,采用超前导洞应力释放工法相对常规三台阶法可明显减小衬砌结构的受力,表明挤压性围岩小间距隧道采用超前导洞应力释放的方法在理论和实践上是可行的。

For the small-spacing tunnel,tube group effect and stability of middle rock pillars are the main challenges,especially in squeezing rocks,it will result in that cracks occur earlier in the first excavated tunnel tube and then cracks occur at the right tube while construction is taken on the left tube.Based on the Xinchengzi tunnel which is a typical case of large deformation at the bellmouth-shape exit section in squeezing rock mass,a construction method of stress release with advanced pilot tunnel was proposed,and the effect was verified by comparison of structure test results and numerical analysis.The results show that compared with the conventional three-bench method,the forces acting on lining structure significantly decrease by using advanced pilot tunnel method to release stress,so it is practical both in theory and practice for the small-spacing tunnels in squeezing rock mass to use advanced pilot tunnel to release stress.