An analysis of the settlement of a shield tunnel passing under the operating railway bridge
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摘要: HTSS以大连地铁2号线香沙区间盾构隧道下穿铁路桥特殊地段为依托，通过三维有限元程序仿真模拟以及工程现场动态监测，研究盾构施工法对周围地层变形的影响和盾构下穿铁路桥造成的沉降特征。结果表明：盾构开挖引起的地表沉降经历了5个阶段，即初期扰动沉降、开挖面前部沉降、盾构机正上方沉降、盾构通过沉降、后期固结沉降；地表沉降整体为一个凹槽形，即隧道中心线地表沉降大，隧道两边沉降较小，按隧道横截面轴线左右对称，符合地表沉降机理，并与现场监测数据一致；距离开挖隧道越近，总体沉降位移越大，盾构开挖小于20 m时，其沉降位移沿着横向与纵向都有扩展，隧道开挖至40 m时，沉降位移主要沿着纵向扩展，横向扩展不明显；不同深度的上部土体沉降呈漏斗形，即隧道正上方沉降最大，两边沉降递减，沉降曲线基本对称，地表右侧受右线隧道开挖影响，沉降量略大于左侧；桥桩底端处于隧道拱顶上，且整个桩身处于破裂面之上，属于短桩范畴，桥桩变形主要以受土体作用而产生的竖向沉降变形为主。Abstract: Research on the shield tunnel of the Xiang-Sha bid section of Dalian metro is done to analyze the effect of the surface settlement by 3D finite element simulation, combined with in situ monitoring data. The results show that the surface settlement undergoes five stages: initial disturbance settlement, settlement in front of excavation, settlement above shield machine, settlement of shield passing and consolidation settlement. The overall shape of the surface settlement is a groove, the surface settlement of the central line of the tunnel is large, and the settlement of both sides of the tunnel is small. The settlement is symmetrical with the axis of the cross section of the tunnel, which conforms to the mechanism of the surface settlement and is consistent with the field monitoring data. The closer the tunnel is to be excavated, the larger the overall settlement displacement is. When the shield excavation is less than 20 m, the settlement displacement expands both horizontally and longitudinally. When the tunnel is excavated to 40 m, the settlement displacement mainly expands along the longitudinal direction, but the lateral expansion is not obvious. The funnel-shaped subsidence is the largest on top of the tunnel, and it decreases on two sides. The settlement curve is basically symmetrical, but the settlement on the right side is slightly larger than the left side because of the excavation of the right line tunnel. The whole pile is on the fracture surface of the tunnel, it belongs to the category of short piles and the deformation of the bridge pile is mainly caused by the vertical settlement of soil.
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Key words:
- large shield /
- metro construction /
- railway bridge /
- surface settlement /
- tunnel /
- 3D finite element
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