基坑开挖对近邻运营地铁隧道影响规律研究

Influence of foundation pit excavation on adjacent metro tunnels

对某邻近基坑开挖的地铁隧道的水平位移和沉降的时空分布做了深入分析。由于软土的蠕变效应,应考虑基坑分块开挖的先后顺序造成的时空效应的影响,以及基坑围护体系的水平支撑结构对土体位移的限制作用。基坑开挖对邻近地铁隧道的影响范围为2.5倍开挖深度,而对于远基坑的右线,影响范围更低,甚至低至1.5倍开挖深度。将基坑和隧道的监测数据联系分析,得到比值与水平距离的关系曲线,将基坑监测数据代入拟合公式,对地铁水平和垂直位移进行估算。隧道水平位移与邻近的同深度土体水平位移的比值（Ω）,其最大累计位移点的Ω较多地处在0.60-0.65范围,在底板浇筑都已完成后,稳定在0.60。隧道沉降与邻近地表沉降的比值（θ）,其最大累计沉降点的θ,较多地处在0.50~0.60间,底板浇筑完成后,稳定在0.52±0.05水平。

The spatial and temporal distribution of the horizontal displacement and settlement of a metro tunnel adjacent to the foundation pit is analyzed. Due to the creep effect of the soft soil, the space-time effect caused by the excavation of the foundation pit should be considered, in addition to the limit of the horizontal support structure of the foundation pit supporting system. The influencing scope of excavation on adjacent metro tunnel is 2.5 times the depth of excavation, and for the right line far away from the foundation pit, the influence scope is smaller, even lower to 1.5 times the depth of excavation. Based on the monitoring data of foundation pit and adjacent tunnels, the ratio-horizontal distance relation curve is obtained. Then the horizontal and vertical displacements of tunnel are estimated based on the monitoring data of foundation pit and fitting formula. The ratio between horizontal displacement of tunnel and that of the adjacent soil at the same depth, which corresponds to the maximum accumulative displacement, generally ranges from 0.60 to 0.65, and becomes stabilized at 0.60 after the foundation slab casting is finished. The ratio between settlement of tunnel and that value of the adjacent earth＇s surface, which corresponds to the maximum cumulative settlement, is largely located within the range from 0.50 to 0.60, and becomes stable at the level of 0.52±0.05.