双连拱地铁隧道施工关键技术及力学行为模拟

研究目的:本文依托西安地铁5号线雁鸣湖停车场段双连拱隧道浅埋暗挖工程,结合该工程中导洞+上下台阶施工方法,探讨双连拱地铁隧道在黄土地区应用的关键技术,并从地表沉降、对既有隧道影响、新建隧道衬砌应力变化及变形规律四个方面论述双连拱隧道施工的力学行为变化规律。研究结论:(1)受中导洞分割作用,左、右正洞施工相互影响微弱,其初衬变形规律基本相同,双连拱隧道施工引起的地表沉降可以认为是中导洞、右洞、左洞独立开挖引起的地表沉降的叠加;(2)当前施工方案下既有隧道主要产生整体性偏移,最大水平位移及竖向位移分别为7.2 mm、5.5 mm,而其最大拱腰收敛量仅为2.25 mm,最大应力变化量仅为0.35 MPa;(3)初衬拱顶沉降可分为三个阶段:迅增阶段、缓增阶段、稳定阶段,其中迅增阶段(超过监测断面2倍洞径以内)为施工过程中的关键阶段,施工过程中应加强监测,并根据实测数据采取相应保护措施;(4)初衬施工过程中,随着后行洞的开挖,中隔墙受力逐渐对称,墙中心水平偏移及墙角应力偏差减小,初衬施工结束时中隔墙受力及变形已基本恢复对称;(5)本研究可为黄土地区城市地铁双连拱隧道施工关键技术及力学行为规律的进一步研究提供有益参考。

Key Technology and Mechanical Behavior Simulation of a Double-arch Subway Tunnel

Research purposes:This paper relied on the shallow excavation project of double-arch tunnel in the Yanming Lake parking lot of Xi’an subway line 5.Combined with guide tunnel and benching tunneling construction method,the key technology of double-arch subway tunnel applied in loess area was discussed,and the mechanical behavior of double-arch tunnel construction was studied from four aspects:surface settlement,influence on the existing tunnel,the rules of change of lining stress and deformation of new tunnel.Research conclusions:(1)Due to the segmentation of the middle guide hole,there is a weak mutual influence between the right and left main holes,and the deformation law of the initial lining is basically same.The surface settlement caused by the construction of double-arch tunnel can be considered as the superposition of the surface settlement caused by the independent excavation of the middle guide hole,right hole and left hole.(2)Existing tunnels under the current construction scheme mainly produce overall migration,with the maximum horizontal displacement and vertical displacement being 7.2 mm and 5.5 mm respectively,while the maximum convergence of hance is only 2.25 mm,and the maximum stress variation is only 0.35 MPa.(3)The settlement of initial lining vault can be divided into three stages:rapid increasing stage,slow increasing stage and stable stage.The rapid increase stage(which is within 2 times of the tunnel diameter beyond the monitoring section)is the key stage in the construction process.During the construction process,monitoring should be strengthened and corresponding protective measures should be taken according to the measured data.(4)Along with the excavation of following holes,the stress on the mid-partition is gradually becoming symmetrical,and the horizontal offset of the center of mid-partition and stress deviation of the corner is decreasing.At the end of the construction of the primary lining,the stress and deformation of the mid-partition have basically returned to be symmetrical.(5)The research result can provide a useful reference for the further research on the key technology and mechanical behavior of the construction of urban subway double-arch tunnel in loess region.