黄土地区暗挖车站扣拱优化与现场监测研究

Research on Arch Buckle Optimization and Field Monitoring of Underground Excavation Station in Loess Area

为探究黄土地区PBA车站扣拱施工顺序诱发的地表沉降及围岩应力变化规律,采用有限差分软件FLAC 3D建立暗挖地铁车站三维计算模型,完成扣拱施工诱发围岩应力变化及地表沉降预测及现场试验监测分析。数值模拟表明:4种施工顺序引起的地表沉降最大沉降均位于车站中心线,沉降曲线呈“V”型,“先中后边”错距开挖拱顶累计位移、围岩应力及诱发的地表沉降最小;扣拱“先中后边”错距施工,深层土体位移较小,土体结构变化及相互作用力变化较小,有效地减弱了底板隆起对导洞施工的影响,便于控制地表沉降,有利于施工安全;基于扣拱“先中后边”错距施工顺序,制定暗挖车站扣拱施工期间的扣拱受力与地表沉降现场监测方案。工程实践表明,实测曲线与FLAC 3D模拟结果基本吻合,FLAC 3D预测计算合理可行。

In order to explore the variation law of surface settlement and surrounding rock stress induced by the arch construction sequence of PBA method underground excavation station in loess area,a three-dimensional calculation model of subway underground excavation station is established by using the finite difference software FLAC 3D,and the surrounding rock stress changes and surface settlement prediction analysis induced by different arch construction sequences are completed.FLAC 3D prediction shows that the maximum settlement of ground settlement caused by the four construction sequences is located in the center line of the station,and the settlement curve is V-shaped.The cumulative displacement,the stress of the surrounding rock and the induced ground settlement are the smallest for the“sides after central”excavation of the arch crown with staggered spacing constructing sequence.For the“sides after central”excavation of the buckle arch,the displacement of deep soil is small,the change of soil structure and the change of interaction force are small,and the influence of floor heave on the construction of pilot tunnel is effectively weakened,which is convenient to control the surface settlement and is beneficial to the construction safety.Based on the staggered construction sequence of the arch“first middle and then side”,the on-site monitoring scheme of the arch stress and surface settlement during the construction of the arch of the underground excavation station is formulated.The engineering practice shows that the measured curve is basically consistent with the FLAC 3D simulation results,and the FLAC 3D prediction calculation is reasonable and feasible.