地铁隧道盾构下穿富水粉土层时地层及管片变形规律

Deformation Law of Stratum and Segment During Metro Shield⁃driven Tunnel Undercrossing Water Rich Silt Stratum

针对盾构下穿富水粉土层容易造成地表沉降、盾构姿态难以控制等问题,以徐州地铁2号线新元大道—新区东站区间下穿故黄河富水粉土层盾构施工为工程背景,建立有限元模型,结合现场监测情况,研究了富水粉土层中盾构开挖对地层及管片变形的影响规律。结果表明:盾构机掘进过程中,对于横断面,地表沉降曲线近似为正态分布曲线,影响半径约16~20 m;对于纵断面,对开挖面前方的地表沉降影响区域约14 m,最大地表沉降发生在盾尾注浆的上方;管片竖向变形主要集中在拱顶与拱底处,且拱顶沉降,拱底上浮;管片水平方向变形主要集中在拱侧中上部与中下部,且管片整体向内收敛;造成管片上浮的因素主要有盾尾空隙、地层特性、地基回弹、施工参数等。

Aiming at the problems of ground settlement and shield posture difficult control caused by shield-driven tunnel undercrossing water rich silt stratum,taking the shield construction of Xuzhou Metro Line 2 from Xinyuan avenue to Xinqu east station undercrossing the Abandoned Yellow River water rich silt stratum as the engineering background,the finite element model was established,and the influence of shield excavation on stratum and segment deformation in water rich silt stratum was studied based on field monitoring.The results show that in the process of shield tunneling,for the cross section,the ground settlement distribution curve is approximately normal distribution,and the influence radius is about 16~20 m.For the vertical section,the influence area of ground settlement in front of the excavation face is about 14 m,and the maximum ground settlement occurs above the shield tail grouting.The vertical deformation of segment is mainly concentrated in the vault and arch bottom,and it settles at the vault and floats at the arch bottom.The horizontal deformation of the segment is mainly concentrated in the upper and middle part of the arch side,and the segment converges inward as a whole.The main factors causing segment floating are shield tail gap,stratum characteristics,foundation rebound,construction parameters and so on.