大跨度市政通道开挖近接轨道交通隧道变形特性分析

Analysis on Deformation Characteristics of Excavating Long-span Municipal Underpass Adjacent to Metro Tunnel

为确保大跨度市政通道近接轨道交通线路结构安全,基于市政通道近接轨道交通已建成6号线及未建8号线工程,建立了三维有限元模型,分析了近接通道及轨道交通6号线隧道结构变形规律,并与实测数据对比,明确了施工及加固方案的实施效果。针对市政通道上穿轨道交通6号线施工,选取分区围护结合分步开挖的施工方案进行了分析。结果表明:在隧道正上方通道基坑(E区)开挖时,竖向隆起变形虽然逐步增大,但该施工阶段增大变化率明显小于前几个区段的大范围分块开挖方案;市政通道基坑开挖引起的地表较大变形出现在基坑开挖位置,最大为19.7 mm;6号线隧道结构竖向最大变形为13.3 mm,隧道结构的最大水平变形0.61 mm;隧道钢轨所在长度范围内(10 m)最大差异变形为1.4 mm;隧道结构最大相对曲率半径为35714 m,最大水平净空收敛为0.3 mm,最大竖向净空收敛为0.5 mm,各项指标皆满足控制指标要求,且现场监测数据与数值模拟计算结果吻合度较好。针对规划轨道交通8号线下穿市政通道,选取下穿区域旋喷桩加固并在两侧设置防沉桩方案进行了分析。结果表明:轨道交通8号线隧道施工完成后,市政通道竖向最大位移为8.8 mm,水平最大位移为1.1 mm,变形缝最大差异沉降为1.1 mm;采取基底加固和设置防沉桩措施后,后续8号线隧道结构施工导致的通道结构的变形可控,满足控制标准的要求。

In order to ensure the structural safety of long-span municipal underpass adjacent to rail transit line,based on the municipal underpass project adjacent to the existing subway line 6 and planned subway line 8,a 3 D FE element model is established,the structural deformation rule of the adjacent underpass and rail transit line 6 is analyzed,which is compared with the measured data to clarify the implementation effect of the construction and reinforcement scheme.For the construction of municipal underpass over subway line 6,the construction scheme of zoning enclosure combined with stepwise excavation is selected and analysed.The result shows that(1)although the vertical uplift deformation increases gradually during the excavation of the foundation pit(area E)directly above the tunnel,the increase rate in this construction stage is obviously less than that of the large-scale block excavation scheme in the previous sections;(2)the large surface deformation caused by the excavation of the foundation pit of the underpass occurs at the excavation position of the foundation pit,and the maximum is 19.7 mm;(3)the maximum vertical deformation of the tunnel structure of line 6 is 13.3 mm,and the maximum horizontal deformation of the tunnel structure is 0.61 mm;(4)the maximum differential deformation within the length range of the rail(10 m)in the tunnel is 1.4 mm;(5)the maximum relative curvature radius,the maximum horizontal clearance convergence and the maximum vertical clearance convergence of the tunnel structure are 0.3,0.5,35714 m respectively.All the indicators meet the requirements of control indicators,and the on-site monitoring data is in good agreement with the numerical simulation calculation result.For the municipal underpass beneath the planned subway line 8,the scheme of rotary jet grouting pile reinforcement in the underpass area and setting anti sinking piles on both sides is selected and analysed.The result shows that(1)after the construction of the tunnel of subway line 8 is completed,the maximum vertical displacement,the maximum horizontal displacement and maximum differential settlement of the deformation joint of the municipal passage are 8.8,1.1,1.1 mm respectively;(2)after taking the measures of base reinforcement and setting anti sinking piles,the deformation of the underpass structure caused by the subsequent construction of tunnel structure for subway line 8 is controllable,which meets the requirements of the control standard.