新建车站密贴下穿既有车站施工方法研究

Research on the construction method of the newly-built station closely pasting and passing the existing station

以北京地铁6号线西延线工程苹果园站密贴下穿既有车站工程为背景,对新建车站施工方法进行研究。采用有限元分析软件迈达斯GTS-NX软件分别对中洞法、侧洞法、柱洞法及PBA法四种常用浅埋暗挖施工方法的施工过程进行模拟,对比分析不同施工方法对地表沉降、既有车站结构变形、既有车站轨道结构变形及围岩塑性区分布的影响,其结果表明:首次开挖对地层扰动是最大的,且引起的地表沉降在整个施工过程也是占比最大的,PBA法施工对地表沉降控制效果最好,中洞法、柱洞法次之,侧洞法控制效果最差;不同施工方法引起的既有车站结构沉降趋势相同,靠近施工断面的沉降大,远离施工断面的沉降小;不同施工方法下既有车站轨道结构沉降规律是不相同的,中洞法、柱洞法受群洞效应的影响大,曲线呈不均匀性,而侧洞法和PBA法受群洞效应影响小,曲线较均匀;四种工法施工引起的塑性区均在车站周围,除PBA法外,其余工法的塑性区均已侵入车站内部,会影响既有车站的安全;最终通过实测数据与数值模拟结构的对比分析,验证了数值模拟的准确性。

Taking the existing station project of Ping Guoyuan station of Beijing Metro Line 6 west extension project as background,the construction method of new station is studied.Finite element analysis software Midas GTS-NX software was used to simulate the construction process of four commonly used shallow and dark excavation construction methods,namely middle tunnel method,side tunnel method,column tunnel method and PBA method,and analyze the influence of different construction methods on surface settlement,existing station structure deformation,existing station track structure deformation and surrounding rock plastic zone distribution.The results show that:The ground disturbance caused by the first excavation is the largest,and the surface settlement caused by the first excavation is also the largest in the whole construction process.The PBA method has the best control effect on the surface settlement,followed by the middle tunnel method and the column tunnel method,and the side tunnel method has the worst control effect.The settlement trend of existing station structure caused by different construction methods is the same,the settlement near the construction section is large,and the settlement far away from the construction section is small.The settlement law of existing station track structure is different under different construction methods.The middle hole method and column hole method are greatly affected by group hole effect and the curve is not uniform,while the side hole method and PBA method are less affected by group hole effect and the curve is more uniform.The plastic zones caused by the four construction methods are all around the station.Except for PBA method,the plastic zones of other construction methods have invaded into the station interior,which will affect the safety of the existing station.Finally,the accuracy of numerical simulation is verified by comparing the measured data with the numerical simulation structure.