双孔平行地铁隧道盾构施工地表沉降分布规律研究

Distribution Laws of Surface Settlement Induced by Shield Construction of Twin-Tube Metro Tunnels

盾构法施工中不可避免地会对周围地层产生扰动影响,故加强盾构施工变形控制显得尤为重要。文章以某城市地铁盾构隧道工程为研究背景,采用理论分析和数值模拟方法,研究了双孔平行隧道施工地表沉降分布规律及影响因素,提出了改进的双线隧道地表沉降预测方法,并与现场实测数据进行了对比分析。研究结果表明:隧道间距越大,形成"W"形沉降曲线特征越明显;隧道埋深越小,沉降曲线由"V"形向"W"形转变所需的隧道间距L越小;土质条件越好,地层扰动影响范围越小,"W"形沉降槽特征也越显著;采用C=L/2i来描述双线平行隧道地表沉降分布特征是可行的,随C值增大地表沉降曲线分布由"V"形—"锅底"形—"W"形发展,"W"形非对称性分布特征与隧道相对间距有关;由本文提出的双线盾构施工引起的地表沉降计算公式计算出的地表沉降预测值与实测沉降曲线吻合较好,可用于双线隧道施工地表沉降变形预测,对盾构隧道研究具有重要理论指导和实践意义。

It is inevitable for shield construction to disturb surrounding strata, and it is particularly important to control deformation induced by shield construction. Based on a metro shield tunnel project, the laws of surface settlement for a twin-tube tunnel are studied by a theoretical analysis and numerical simulation, a modified ground settlement prediction method for twin-tube tunnels is put forward, and a comparison between theoretical data and measured data is conducted. The study results show that the larger the tunnel tube interval, the more obvious the ＂W＂- shaped curve of the settlements; the smaller the tunnel overburden, the smaller the interval L required for the trans- formation from a ＂V＂-shaped curve to a ＂W＂-shaped curve of settlements; the better the soil conditions, the smaller the scope of disturbed strata and the more obvious the features of the ＂W＂-shaped settlement trough; it is possible to use C=L/2i to describe the surface settlement distribution features of the twin-tube tunnel, and the surface settlement distribution curve develops from a ＂V＂ shape to that of a ＂Pot＂ and ＂W＂ with an increase of C, and the unsymmetrical ＂W＂-shaped distribution is related to the relative interval of the tunnel tubes; and the predicted surface settlements calculated by the proposed formula agree well with the measured settlements induced by the construction of twin-tube tunnels.