考虑地层蠕变效应的桥梁桩基施工对邻近运营地铁隧道的影响

为研究桥梁桩基施工引起地层蠕变行为对邻近地铁隧道安全运营的影响,依托实体工程,采用卸荷条件下黏土蠕变特性试验确定了隧道周围土体的蠕变模型,通过数值模拟手段(FLAC3D软件)与现场监测相结合的方法,分析了桩基开挖期间地铁隧道的竖向位移、水平位移和应力分布状态。结果表明：广义Kelvin本构模型能够较为准确的描述黏土体开挖卸荷时的蠕变效应；桩基开挖后,邻近地铁隧道衬砌位移不断增大,随后进入稳定状态；随着桩基开挖数量的增加,地铁隧道竖向位移和水平位移总体表现为下沉和向外收敛趋势；桩-隧最小净距越小,桩基施工对隧道影响越大,采用隧道双侧布桩的施工方式,能够有效降低桩基开挖时隧道拱腰的累计水平位移,有利于地铁隧道的安全稳定运营。

Study on the influence of the construction of the bridge pile foundation on the adjacent operating subway tunnel considering creep characteristics of stratum

To comprehensively investigate the impact of the stratum creep effect caused by the construction of bridge pile foundation near the operated subway tunnels, the soil constitutive numerical model was determined by the creep tests under unloading conditions. Meanwhile, the numerical simulation (FLAC3D software) and field monitoring were combined to analyze the vertical displacement, horizontal displacement and stress distribution of subway tunnels during the pile foundation excavation. The results showed that the generalized Kelvin model can accurately describe the creep effect of clay soil in excavation unloading. During pile excavation, the lining displacement of the adjacent subway tunnel increased continuously and then settled into a steady state. With the increase of pile excavation, the vertical and horizontal displacements of subway tunnels presented a sinking and outward trend, and the smaller the minimum distance between pile and tunnel, the greater the influence of the pile foundation construction on the tunnel. The construction method of arranging piles on both sides of the tunnel can effectively decline the accumulated horizontal displacement of the tunnel haunch during pile foundation excavation, which is conducive to the safe and stable operation of the subway tunnel.