实验技术与管理2025，Vol.42Issue(12)：35-44,10.DOI:10.16791/j.cnki.sjg.2025.12.005
分岔隧道双洞过渡至单洞大跨段施工工法研究
Construction method for transitioning twin tunnels to a single tunnel at a large-span section of a bifurcated tunnel
摘要
Abstract
[Objective]This study aims to investigate the spatial mechanical characteristics of bifurcated tunnels and optimize construction methods.The study conducts a comparative analysis of construction techniques that account for the gradual change in clear distance between the leading and subsequent tunnels while employing both gradual expansion excavation and sudden change excavation methods in the transition section.The research is based on the Dashanpo tunnel of the Chongqing-Kunming high-speed railway.[Methods]FLAC3D numerical simulations were used to replicate the excavation process under on-site conditions.By integrating stress and strain monitoring of the lining structure with displacement monitoring of the surrounding rock,the mechanical and deformation behaviors of the surrounding rock and tunnel lining structure under both gradual expansion and sudden change excavation methods for this type of bifurcated tunnel were compared and analyzed.[Results]The results show that the gradual expansion excavation method effectively controls surrounding rock deformation at the point of sudden cross-section change,reducing maximum displacement by 39.81%compared to the sudden change method.The trend of the tunnel vault remains consistent and increases from the double-hole section to the large-span section before and after optimization.The area of influence extends 9 m before and after the sudden cross-section change,with the maximum difference in settlement occurring over 3 m from the sudden change to the large-span section.After optimization,the maximum minimum principal stress in the tunnel's preliminary lining is reduced by 27%.The bending moment difference between the left and right arch feet of the preliminary lining at Section I under the gradual expansion method is reduced by 41.7%compared to the sudden change method.In Section II,the bending moment is also significantly affected by excavation,showing reductions of 69.3%and 52.1%,respectively.The axial force difference between the left and right arch feet in tunnel Sections I and II under the gradual expansion method is reduced by 49.3%and 52.7%,respectively.[Conclusions]The results demonstrate that under the sudden excavation method,significant vertical displacement occurs in the surrounding rock at the sudden cross-section change of the bifurcated tunnel,primarily concentrated at the arch waist of the double-tunnel section.The gradient expansion method effectively controls deformation in this section of the tunnel.In addition,this method yields a more favorable transition in the preliminary lining's stress state,thereby improving the uneven force distribution of the support structure,particularly at the arch foot.Consequently,it can be concluded that the gradient expansion method is the optimal construction technique for transitioning from double-tunnel to single-tunnel large-span sections in bifurcated tunnels.The study's findings provide valuable insights for future similar engineering projects.关键词
分岔隧道/数值模拟/影响规律/现场监测/力学特性Key words
bifurcated tunnel/numerical simulation/influence law/on-site monitoring/mechanical properties分类
交通工程引用本文复制引用
WANG Chaozhen,WANG Qiaoyu,FU Boyi,MIAO Zengrun,LIU Yongde,ZHANG Huijian,WANG Mai..分岔隧道双洞过渡至单洞大跨段施工工法研究[J].实验技术与管理,2025,42(12):35-44,10.基金项目
国家自然科学基金项目(52178395) （52178395）
