铁路上下重叠隧道施工力学特性研究

Research on the Mechanical Characteristics of Overlapping Tunnel Construction on Railways

随着我国道路交通工程建设的快速发展,不断有上下或交错重叠布置的高难度隧道工程涌现。本文依托重庆东环线铁路芭蕉沟上下重叠隧道工程,针对不同典型断面建立了多个数值模型,研究了重叠隧道施工历程中隧道拱顶位移、仰拱变形和横撑处水平收敛的变化规律以及相应的非同步开挖条件下的隧道衬砌应力分布特征,并且结合施工引起的地层应力变化规律以及塑性区分布特征分析了开挖过程的地层扰动效应。结果表明:(1)不同断面处的上层隧道施工主要引起下层隧道的拱顶沉降与净空收敛,而对仰拱部分影响较小,施工中应重点关注拱顶沉降与净空收敛;(2)当上、下层隧道相距较近时,上层隧道施工会导致下层隧道一定程度隆起,随两隧道之间距离的增加,回弹程度逐渐降低直至沉降。据此提出相应的施工扰动控制措施,从而为优化结构设计和指导现场施工服务,并可为今后类似工程提供借鉴与参考。

With the rapid development of tunnel construction in China,there are constantly emergence of high-difficulty tunnel projects with overlapping or staggered arrangements.Based on the overlapping tunnel project of the upper and lower layers of Bajiaogou on the Chongqing East Ring Railway,through the method of numerical simulation,a number of working conditions have been established for different typical cross-sections,and the changing laws of tunnel vault displacement,invert deformation and horizontal convergence of transverse braces during the construction of overlapping tunnels,and stress distribution characteristics of secondary lining under corresponding non-synchronous excavation conditions are studied.And combined with the law of formation stress change caused by construction and the distribution of plastic zone,the stratum disturbance effect of the excavation process is analyzed.The results show that:(1)The construction of the upper tunnel at different sections mainly caused the settlement of the vault and the convergence of the clearance of the lower tunnel,but the impact on the invert part was small.The construction should focus on the settlement of the vault and the convergence of the clearance;(2)When the upper and lower tunnels are close to each other,the construction of the upper tunnel will cause the lower tunnel to bulge to a certain extent,but with the increase of the distance between the two tunnels,the rebound degree will gradually decrease until settlement.Based on this,the corresponding construction stratum disturbance control measures are proposed,so as to optimize structural design and guide on-site construction services,and provide reference and reference for similar projects in the future.