埋深对大管幕支护隧道下穿高速公路施工的地表沉降影响研究

Research on Influence of Buried Depth under Large Pipe Curtain on Surface Subsidence of Tunnel Construction

以重庆铁路枢纽东环线新白杨湾下穿高速公路隧道工程为依托,研究了大管幕支护下隧道埋深对下穿高速公路地表沉降的影响。采用有限元分析软件MIDAS-GTS NX建立隧道施工模型,分析埋深分别为2.5m、3m、4m、6m、10m、和15m共6种工况下地表沉降、围岩变形以及初衬内力等力学特性的变化规律,并通过模拟值和实测值对比确定本文方法的正确性。研究结果表明:随着埋深的增大,隧道的施工对地表沉降影响范围逐渐增大,沉降最大值逐渐减小,埋深超过15m时,地表沉降值基本不受埋深的影响。地层损失率随着埋深的增大而减小,当埋深超过一定深度时,隧道的开挖对地层扰动较小且扰动范围基本不变。埋深从2.5m增加到3m时,水平位移变化较小,埋深超过3m以后,水平位移迅速减小,埋深超过15m时水平位移值保持基本不变。初支应力随埋深先增大后减小,埋深3m时应力达到最大值。通过模拟值和实测值的对比分析可知,有限元结果合理且可靠,指导了本工程施工,对类似工程有指导意义。

Relying on the highway tunnel project of the Xinbaiyangwan under the east ring line of Chongqing railway hub,the influence of the burial depth of the tunnel supported by the large pipe curtain on the ground set⁃tlement of the expressway passing through it is studied.The finite element analysis software MIDAS-GTS NX is used to establish the tunnel construction model,analyze the change laws of mechanical characteristics such as ground settlement,surrounding rock deformation,and initial lining internal force under 6 operating conditions at 2.5m,3m,4m,6m,10m,and 15m,the correctness of the method in this paper is determined by comparing the simulated and measured values.The research results show that with the increase of the burial depth,the influ⁃ence range of the tunnel construction on the surface settlement gradually increases,and the maximum settlement gradually decreases.When the burial depth exceeds 15m,the surface settlement value is basically not affected by the burial depth.The formation loss rate decreases with the increase of the burial depth.When the burial depth exceeds a certain depth,the excavation of the tunnel has a small disturbance to the formation and the dis⁃turbance range is basically unchanged.When the burial depth is increased from 2.5m to 3m,the horizontal dis⁃placement changes little.After the burial depth exceeds 3m,the horizontal displacement decreases rapidly.When the burial depth exceeds 15m,the horizontal displacement value remains basically unchanged.The initial support stress first increases and then decreases with the burial depth.The stress reaches a maximum at a burial depth of 3 m.The comparative analysis of the simulated and measured values shows that the finite element re⁃sults are reasonable and reliable,which guides the construction of this project and has guiding significance for similar projects.