兰州市轨道交通1号线是从西向东通过兰州市蜂腰地段的一条主干交通线路，横贯中心城区。1号线地铁隧道下穿既有鱼儿沟桥，与其桩基相互影响，故隧道施工前必须对鱼儿沟桥进行桩基托换。本文采用有限元软件 MIDAS/GTS建立三维有限元模型，对隧道下穿鱼儿沟桥的开挖以及切桩过程进行了数值模拟，分析了隧道开挖和切桩过程中桩基和土层的力学行为。计算结果表明：既有鱼儿沟桥通过地面桩基托换，洞内截桩后，地表沉降、桩基沉降、桩基受力均满足规范要求，桩基托换方案合理可行。%As the main transport corridor in Lanzhou,the No. 1 transit line extends from the west to the east,running through the most crowded downtown area of the city. As the metro tunnel passes under the existing Yu'ergou bridge,the pile foundations of the two inevitably interplay,in which case enhancement treatment is needed before the construction. Applying the finite-element software M IDAS/GT S,a 3D finite-element model was built to carry out numerical simulation on the mechanical behavior of the piles and the soil layer amid tunnel excavation and pile cutting. T he results indicate that enhancement treatment is a valid solution,which by underpinning ground piles and cutting piles in the tunnel ensures that ground subsidence,foundation settlement and force-bearing of piles all meet the requirement concerned.
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