单线隧道大型机械化快速施工步距优化研究

Research on Optimal Construction Step of Large Mechanized Rapid Construction of Single Track Tunnel

以太锡铁路太崇段的和平隧道与崇礼隧道工程项目为依托,利用FLAC3D数值模拟软件建立隧道开挖过程中衬砌和仰拱不同施工步距模型,结合工程地质特点研究仰拱和二衬的不同步距对隧道开挖安全性的影响效应,并探讨在机械化快速施工要求下,隧道在不同级别围岩施工时仰拱和二衬的施作步距。分析结果表明,在不同级别围岩条件下,由仰拱开挖所引起的围岩收敛累计变形大部分在2~3 mm之间,且围岩变形逐渐趋于稳定;在仰拱步距相同情况下,不同二衬施作步距工况下的围岩累计收敛变形和未施作二衬工况相比,围岩变形相差不大,均偏于安全。通过数值计算分析并结合实际工程情况,该项目最终将Ⅲ级、Ⅳ级围岩和Ⅴ级围岩的仰拱步距调整为120 m、100 m,衬砌步距调整为170 m、150 m,不仅保证了施工的安全性,而且极大地节省了工期,可为今后类似工程提供借鉴。

Based on the project of Heping and Chongli tunnels in Taichong section of Taizicheng-Xilinhot Railway,FLAC3 Dnumerical simulation software was used to establish the model of different construction steps of lining and invert in the process of tunnel excavation,the effect of different construction steps of invert and secondary lining on the safety of tunnel excavation under the geological characteristics of the project was studied.The construction steps of invert and secondary lining in different levels of surrounding rock under the mechanized rapid construction was discussed.The analysis results show that:in the construction of the project under different levels of surrounding rock,the accumulated convergence deformation of surrounding rock caused by invert excavation is mostly between 2~3 mm,and the deformation of surrounding rock gradually tends to be stable;under the same invert step,the accumulated convergence deformation of surrounding rock under different secondary lining construction step is similar to that without secondary lining construction,and the deformation of surrounding rock tends to be safe.Through the numerical calculation and combined with the actual engineering situation,the invert step of gradeⅢandⅣsurrounding rock and grade V surrounding rock is adjusted to 120 m and 100 m,and the lining step is adjusted to 170 m and 150 m,which not only meets the safety of construction,but also greatly saves the construction period.It can provide reference for similar projects in the future.