地铁盾构隧道下穿施工对简支梁桥安全性影响分析

由于土体挖除、管片和二衬的设置,盾构施工过程中周围地层土体的初始状态会受到影响,导致上部结构产生不均匀沉降及横向位移,影响桥梁运营。结合盾构下穿既有线工程,采用Midas/GTS软件对盾构下穿结构进行建模计算,分析施工引起的桥墩和桥台的沉降特征。结果表明:地铁盾构掘进过程中右桥洞东2号-北侧桥墩(第32步开挖)沉降最大,为6.8 mm;相邻墩台的最大沉降差产生在右线开挖过程中西0-西1、西1-西2、西2-东2墩台(第32步开挖)开挖结束时,为2 mm。在此基础上提出下穿施工时维持桥梁稳定应满足的技术指标:墩台均匀总沉降量小于25 mm,相邻墩台的纵向沉降差小于2 mm,同一墩台的横向沉降差小于3 mm,墩台的水平位移小于3 mm。

Security Analysis on Subway Shield Tunneling Passing under Simply Supported Girder Bridge

Due to soil excavation and the setting of pipe piece and second lining in shield tunneling,the initial state of the surrounding soil is influenced during the working process,which leads to uneven settlement and lateral displacement of the bridge superstructure and adversely affects the bridge's normal service.This Paper uses Midas/GTS software to establish the finite element model based on a shield tunneling project passing under an existing railway to analyze the settlement characteristics of piers and abutments.The results indicate that during the process of shield tunneling,the maximum settlement on the right line at the East No.2-North pier(the 32 ndconstruction step) is 6.8 mm; the maximum differential settlement after excavation between adjacent piers during the excavation on the right line of West 0-West 1,West1-West2,West2-East 2 piers(the 32~(nd) construction step) is 2 mm.It is proposed that construction should meet the technical indicators:the total settlement of piers is less than 25 mm,the longitudinal differential settlement of adjacent piers is less than 2 mm,the lateral settlement of the same pier is less than 3 mm and the horizontal displacement of piers is less than 3 mm.