During the engineering construction period,due to the design adjustment,land transfer,lack of funds and other reasons,the extended service of support structures often occurs,thereby increasing the risk of construction,but numerical simulation analysis about this is rare till today.Based on practical engineering example,by using the MIDAS software and choosing reasonable constitutive models,the numerical simulation for supporting structure for excavation is performed.The findings show that the final maximum horizontal displacement appears at the place of the second anchors,and decreases as the axial forces decrease.With the increase of excavation depth,the ground surface settlement and the bottom uplift of excavation increase at the same time.The decay of axial forces fluctuates from 9％ to 37％,and the decay is still distinct after reducing axial forces.The result of numerical simulation coincides basically with that of measurement in the trend,showing that extended use of supporting structure should arouse people's attention.%在工程建设期间,经常会出现由于设计调整、土地转让、建设方资金不足等情况,造成支护结构超期服役现象,从而增加工程风险,但是对其进行数值模拟分析目前比较少见.结合实际工程算例,运用有限元软件MIDAS,选择合理的本构模型,对基坑的支护结构进行了数值模拟.结果表明:基坑最终水平位移最大值出现在第2道锚杆处,且随着拉力减小,基坑的水平位移有所增大;基坑地表沉降和坑底隆起随着开挖深度增加而增大;锚杆轴力随着基坑开挖深度增大,轴力衰减范围为9％～37％,且轴力减小后衰减依然比较明显;数值结果与实测结果趋势相吻合,表明超期服役的基坑工程应引起必要的重视.
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