天津地铁6号线双线平行盾构隧道施工间隔对地表土体变形影响研究

研究双线盾构隧道在不同施工间隔下施工时地表的变形规律,对控制地表整体变形及不均匀变形十分重要。依托天津地铁6号线双线盾构隧道下穿天津西站站场实际工程实例,以铁路线设施的关键变形控制指标为评判依据,研究盾构左右线不同施工间隔下的地表变形分布特性,对比分析间隔距离与地表沉降和不均匀沉降的关系,为双线盾构隧道工程选择合适的施工间隔提供依据,以保证工程安全及地表铁路设施的正常运行。结果表明,不同施工间隔的影响主要表现为掘进过程对地表土体变形的扰动程度及扰动范围的明显差异:对于地表沉降变形而言,施工间隔越小,掌子面处地表土体沉降越快,且左线完全先行时,地表土体的纵向变形范围约为20 m,相较两洞同时施工时变形范围减小约25 m;对于地表不均匀变形而言,左线完全先行施工条件下,地表轨向变形、水平变形、轨距变形最大分别约为1、0.6、0.2 mm,相较两洞同时施工时分别减小0.8、0.2、0.15 mm。因此,对于双线盾构隧道而言,两洞同时施工时最不利于地表变形的控制,而一条隧道完全先行掘进的方案最有利于地表变形的控制。

Effect on Construction Intervals on Deformation Characteristics of Surface Soil during Construction of Twin-tube Shield-bored Tunnels: Case Study on a Running Tunnel of Line 6 of Tianjin Metro

Studying the mechanism of the ground surface deformation under different construction intervals of twin tube tunnels has great importance for the control of the overall deformation and the differential deformation of the ground surface. In the paper, the distribution characteristics of the surface soil deformation under different construction intervals are studied, with a twin tube running tunnel on Line 6 of Tianjin Metro crossing underneath Tianjin West Railway Station as an example. In the study, the key deformation control indices of the railway facilities are adopted as the evaluation standard. The relationship between the ground surface settlement/differential settlement and the construction intervals are analyzed, providing reliable basis for choosing suitable construction intervals so as to ensure the engineering safety and the smooth operation of the railway facilities. The results reveal that the construction intervals have obvious impact on the disturbance degrees and disturbance ranges of the ground surface deformation during the tunnel construction. As for the ground surface settlement, the smaller the construction intervals are, the faster the surface settlement at the tunnel face is. The range of the longitudinal deformation of the surface soil is about 20m when the left tube is completely in advance, about 25 m smaller than that in simultaneous construction. As for the differential settlement of the surface soil, when the left tube is completely in advance, the maximum values of the surface deformations in the track direction, horizontal direction and track spacing are 1mm, 0.6mm and 0.2mm respectively, about 0.8mm, 0.2mm and 0.15mm smaller than those in simultaneous construction respectively. Thus, the simultaneous construction of the twin tunnel tubes is the most adverse condition in terms of controlling the surface soil deformation, while accomplishing the excavation of one tube before the construction of the other is the best way to control the surface soil deformation.