Abstract: One metro station by PBA method undercrossed the top bridge, and the three bridge piles above the station were only 0.6m away from the top of the station. Reasonable buckle-arch construction sequence was the key for pile settlement controlling. 3D finite element method midas was used to analyze the variation law of pile displacement, surface subsidence and middle-column displacement under different buckle-arch sequence and different staggered distance between middle span and side span. The research results show that: the middle-column displacement with middle before side span sequence is larger than that with side before middle span sequence, and the pile displacement and surface subsidence can be effectively controlled; taking the three bridge piles closest to the station as the zero point, the transverse influence range of the buckle-arch construction on the bridge piles is about 15m; under the four construction schemes, the maximum differential settlement of bridge piles is basically the same, and the change trend is consistent with the buckle-arch construction step; the absolute settlement and differential settlement of bridge pile caused by buckle-arch construction are within the allowable range, and the upper bridge is in a safe and controllable state; the pile settlement, surface settlement and middle-column displacement of the three-section model with the staggered distance between the middle span and the side span are better than those of the six-section model. After comprehensive comparison and selection, it is suggested that the buckle-arch construction sequence should be middle before the side span, and the staggered distance between the excavation faces of the middle span and the side span should be three-section mode.

Key words: tunnel engineering, metro station, PBA method, numerical simulation, buckle-arch sequence

摘要： 某PBA工法地铁车站下穿跨河桥，车站上方3根桥桩距离车站顶部仅0.6 m，合理扣拱施工工序是桥桩沉降控制的关键。采用三维有限元分析法研究了不同扣拱施工顺序及不同中、边跨开挖面错距下桥桩位移、地表沉降及车站中柱位移的变化规律。研究结果表明：先中后边顺序下车站中柱位移较大，但是桥桩及地表沉降可以得到有效控制；以最靠近车站的3根桥桩为坐标零点，扣拱施工对桥桩横向影响范围为15 m左右；4种施工方案下桥桩最大差异沉降基本相同，且随着扣拱施工步变化趋势一致；扣拱施工引起的桥桩绝对沉降和差异沉降均在允许范围内，上部桥梁处于安全可控状态；中、边跨错距为三段模式的桥桩沉降、地表沉降及中柱位移均优于中、边跨错距为六段模式；经综合比选，扣拱施工顺序建议先中后边，中、边跨开挖面错距建议为三段模式。

关键词: 隧道工程, 地铁车站, PBA工法, 数值模拟, 扣拱顺序