土岩组合地层基坑开挖对下卧隧道变形影响模拟分析

Numerical Analysis of Influence of Foundation Pit Excavation on Deformation of Underlying Tunnel in Soil-Rock Combination Stratum

目的 以济南CBD中心绸带路-礼耕路站区间基坑工程为背景,探究土岩组合地层中基坑开挖对下卧隧道运营安全影响。方法 通过三维数值模拟着重分析土岩组合地层中土岩分界面上下岩土强度参数黏聚力c、内摩擦角φ和弹性模量E、土岩交界面位置、围护桩嵌固深度等变化对隧道变形的影响规律。结果 基坑开挖下卧隧道拱顶和拱底均向上浮动,拱腰向内压缩;当土岩分界面处于基坑开挖范围内时,改变土岩地层强度和刚度参数、围护桩嵌固深度、对隧道变形影响较弱;随着土岩组合地层分界面从基坑范围下移到坑底以下隧道拱顶以上以及隧道开挖范围内,隧道拱顶上浮增幅量会逐渐非线性增大,收敛变形会线性增加。结论 土岩组合基坑开挖相较于纯土层基坑开挖对下卧隧道影响显著减小,但受土岩组合设计参数影响大。

This paper was proposed in order to explore the influence of foundation pit excavation on the operation safety of the underlying tunnel in the soil-rock combination stratum,based on taking the foundation pit engineering between Silk Road and Ligen Road station in Jinan CBD center as the background.Through three-dimensional numerical simulation,the influence of soil strength parameters c,internal friction angle φ and elastic modulus E,the position of soil-rock interface and the embedment depth of retaining pile on tunnel deformation in soil-rock combination stratum were analyzed emphatically.Both the vault and bottom of the tunnel floated upward,and the arch waist compressed inward.When soil rock interface was in foundation pit excavation scope,changing the soil rock formation strength and stiffness parameters,retaining pile built in depth,had less effect on deformation of tunnel rock combination with soil formation interface from which the range down to the bottom of foundation pit and tunnel vault,and within the scope of tunnel excavation,the tunnel vault buoyancy increase growth rate will gradually nonlinear,convergence deformation will increase linearly.The excavation of soil-rock combination foundation pit has less influence on the underlying tunnel than that of pure soil,but it is greatly influenced by the design parameters of soil-rock combination.