不等跨小净距隧道施工力学分析与应用

Mechanical Analysis and Application of Tunnel Construction with Unequal Span and Small Clear Distance

为研究不等跨小净距隧道施工时两隧道相互影响关系,基于大横琴山隧道,建立有限元模型,对各开挖步与不同围岩条件以及开挖顺序引起围岩位移、应力及支护结构轴力、弯矩变化进行分析,得到地表及特征线沉降位移、围岩主应力、支护结构特征点轴力及弯矩。结果表明:施工时大跨度断面隧道上部位移较大,同时其地表沉降极值位于隧道中间偏向大跨度隧道处;中夹岩柱在小跨度隧道侧的水平位移较大,因此在支护时,需要对小跨度隧道侧的中夹岩柱进行水平支护,以防止失稳;对比不同围岩条件变形受力特性,较弱围岩条件下施工时,需要进行不对称支护,同时先施工小跨度隧道较优。

In order to study the interaction between the two tunnels during the construction of unequal span and small clear distance tunnels,the finite element model is established on the basis of the Dahengqinshan Tunnel to analyze the displacement and stress of surrounding rock and the change of axial force and bending moment of supporting structure caused by each excavation step.The vertical displacement of surface and characteristic line,main stress of surrounding rock,axial force and bending moment of characteristic points of support structure are obtained.The results show that during the construction,the displacement of the upper part of the large-span cross-section tunnel is large,and the extreme value of the ground settlement is located in the middle of the tunnel inclined to the large-span tunnel.The horizontal displacement of the rock column in the side of the small-span tunnel is large,so it is necessary to support the rock column in the side of the small-span tunnel horizontally to prevent instability.Compared with the deformation and stress characteristics of different surrounding rock levels,asymmetric support is required for construction in weak surrounding rock conditions,it is better to construct small span tunnel first.