T he excavation of a deep foundation pit in Hangzhou is the engineering background. A three-dimensional numerical model is established using ABAQUS,a finite element software. T he influence of isolation pile's diameter on existing metro tunnel displacement is analyzed. T he results show that,due to excavation of the foundation pit,the vertical displacement of the ultimate tunnel lining is about 4mm and the horizontal displacement is about 1mm. T he numerical simulation results are in good agreement with the measured values. T he maximum displacement of the tunnel lining is located at the bottom of the arch and the minimum value is located at the vault. T he lining displacement tend to be down as a whole. T he displacement of the tunnel lining side near the foundation pit is larger than that of the other side. T he greater the diameter of isolation pile is,the less the influence of the excavation of the foundation pit on existing metro tunnel is.%以杭州市一深基坑工程为背景,采用ABAQUS有限元软件建立三维数值模型,分析隔离桩半径对既有地铁隧道位移的影响.研究结果表明:基坑开挖最终引起了隧道衬砌竖向位移约4 mm,水平位移约1 mm,与实测值相吻合;隧道衬砌位移最大值位于衬砌拱底,最小值位于衬砌拱顶,衬砌变形整体呈沉降的趋势;靠近基坑一侧隧道衬砌总位移比另一侧略大;隔离桩的半径越大,基坑开挖对既有地铁隧道的影响越小.
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