盾构隧道下穿对既有高铁桥梁的影响及其加固方案

Impact of Shield Tunnel Under-passing Existing High-speed Railway Bridge and Its Reinforcement Scheme

目的:盾构隧道掘进会引起周围既有高架桥梁整体结构的不均匀沉降,进而影响其正常使用功能和列车运行安全。对此,以南昌市轨道交通4号线一期工程某区间隧道为背景,分析盾构隧道先后下穿对既有高速铁路桥梁的影响及加固方案分析。方法:运用Midas GTS软件模拟盾构隧道先后下穿高速铁路桥梁的过程。分析高铁桥梁墩台顶部的位移及沉降的发展规律,以及加固前后墩台顶部的变形。结果及结论:盾构掘进对墩台顶沉降影响最大,墩台顶最大沉降约为3.40 mm,最大纵向位移约为2.50 mm;对横向变形影响最小,最大横向位移约为1.00 mm,且影响主要在初掘进阶段;盾构引起的高铁桥梁墩台顶变形随着后期管片安装和注浆有所减小;采取隔离桩+注浆加固措施后,桥墩台顶部产生的最大沉降约为1.54 mm,最大沉降差为0.34 mm,最大纵向位移为1.41 mm;最大墩顶沉降能满足高铁桥梁墩顶沉降的控制标准(3.00 mm)要求,且留有一定的变形裕量,较安全。采用注浆与隔离桩加固措施效果良好,安全可行。

Objective:Shield tunnel excavation causes the overall structure uneven settlement of existing high-speed railway bridges in the surrounding area,thereby affecting their normal functionality and operational safety of train.In this context,based on an interval tunnel of Nanchang Rail Transit Line 4 phase I project,the impact of shield tunnel under-passing existing high-speed railway bridge and the reinforcement schemes are analyzed.Method:The process of shield tunnel under-passing existing high-speed railway bridges is simulated using Midas GTS software.The development law of displacement and settlement on the top of high-speed railway bridge piers and abutments are analyzed,as well as the deformation before and after reinforcement.Result&Conclusion:Shield tunneling has the greatest impact on the settlement of bridge piers and abutments,with a maximum settlement of approximately 3.40 mm and a maximum longitudinal displacement of about 2.50 mm.The impact on lateral deformation is minimal,with a maximum lateral displacement of about 1.00 mm,mainly occurring in the initial excavation stage.The deformation of high-speed railway piers caused by shield tunneling decreases with the subsequent installation of tunnel segments and grouting.After implementing isolation piles+grouting reinforcement measures,the maximum settlement of bridge pier tops is approximately 1.54 mm,with a maximum settlement difference of 0.34 mm and a maximum longitudinal displacement of 1.41 mm.The maximum settlement of the pier and abutment tops meets the control standard requirement(3.00 mm)for high-speed railway bridge pier settlement and allows for a certain deformation margin,being relatively safe.The reinforcement measures of grouting and isolation piles perform well,being safe and feasible.