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该文依托渝昆高铁大山坡分岔隧道段工程，采用数值模拟和现场监测方法，对比并分析了优化前的突变式开挖法和优化后的渐变式扩挖法对围岩和隧道支护结构的力学及变形规律。研究结果表明，渐变式扩挖法对隧道变截面突变处的围岩变形具有明显控制效果，较突变式开挖法位移峰值减小39.81%。两种工法下双洞段至大跨段隧道拱顶沉降变化趋势一致且呈递增趋势，影响区域均为隧道变截面突变处前后9 m范围，且二者沉降最大差值出现在变截面突变处至大跨段3 m范围。相较突变式开挖法，渐变式扩挖法的隧道初支结构主应力峰值减小约27%，隧道断面Ⅰ处初支左右拱脚的弯矩差值降低41.7%，断面Ⅱ处初支弯矩受开挖影响显著，拱腰和拱脚弯矩差值分别降低69.3%和52.1%。渐变式扩挖法下隧道初支Ⅰ、Ⅱ断面的左右拱脚轴力差值分别降低49.3%和52.7%。因此，综合各项指标得出渐变式扩挖法相对更优。
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.
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基本信息:
DOI：10.16791/j.cnki.sjg.2025.12.005
中图分类号:U455.4
引用信息:
[1]王朝振,王侨雨,付柏毅,等.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.DOI:10.16791/j.cnki.sjg.2025.12.005.
基金信息:
国家自然科学基金项目(52178395)