PBA车站扣拱施工顺序对上部跨河桥沉降影响分析

Influence Analysis of Buckle-Arch Construction Sequence of PBA Station on the Settlement of Upper River-Crossing Bridge

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。

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.