双侧壁导坑法隧道施工引起的地表沉降分析

Analysis of ground settlement caused by tunnel construction with double-side wall heading method

以哈尔滨地铁大断面隧道为背景,对双侧壁导坑法施工诱发的地面沉陷及隧道本身的变形规律进行研究。利用MIDAS/GTS建立空间有限元模型,采用数值模拟和实际监测数据相结合的方法,对地表沉降、拱顶下沉进行分析。研究结果表明:地表沉降曲线呈"漏斗"状,且沿开挖导洞中线呈对称分布,影响范围约为2. 5D(D为隧道洞径);左上导洞(1号导洞)、右上导洞(2号导洞)、中上导洞(5号导洞)开挖是引起地表下沉的主要原因;拱顶沉降主要发生在距开挖面15 m(1倍隧道洞径)范围内,最大下沉值为-17. 79 mm,占拱顶总沉降量的66%;采用超前加固的方式控制拱顶下沉效果显著,数值仿真结果与实际监控量测数据吻合较好。MIDAS/GTS有限元数值仿真软件可以有效地预判地层变形。

Taking the Harbin Metro large cross-section tunnel as the background,this article studied the ground subsidence induced by the double-side wall heading construction method and the deformation law of the tunnel itself. A spatial finite element model was established by MIDAS/GTS,and the ground subsidence and vault settlement were analyzed by combining numerical simulation with actual monitoring data. The research results show that: The surface subsidence curve presents a "funnel"shape,and it is symmetrically distributed along the middle line of the excavation pilot tunnel. The influence range is about 2. 5 D(D is the tunnel diameter). The main causes of surface subsidence are the excavation of upper left pilot tunnel(1 #),upper right pilot tunnel(2#) and middle upper pilot tunnel(5#). The settlement of the vault is mainly within 15 m(1 times the tunnel diameter) from the excavation face,and the maximum subsidence value is-17. 79 mm,accounting for 66% of the total settlement of the vault. The effect of controlling the vault sinking is remarkable by adopting the pre-reinforcement method,and the numerical simulation results are in good agreement with the actual monitoring measurement data. MIDAS/GTS finite element numerical simulation software can predict formation deformation effectively.