地铁深基坑开挖对冠梁及周围管线影响研究

The influence of deep foundation pit on the crown beam and its surrounding pipeline in subway

以天津市地铁工程某区间段深基坑工程为背景,对基坑开挖过程中冠梁水平、竖向位移及周围管线竖向位移实际监测数据进行分析,在此基础上,通过大型有限差分软件FLAC-3D建立三维分析计算模型,将模拟分析结果与实际监测结果进行了对比分析.结果表明:数值模拟结果与实际监测数据规律符合较好,在3种工况下,冠梁在竖直方向均表现出向上的位移;模拟曲线趋势较为平缓,而实测曲线的起伏较为明显,但二者的位移差值不大,3种工况下二者的差值分别为3.5 mm、4.0 mm和5.0 mm左右,模拟值与现场监测值均在监测控制值25 mm的范围内;冠梁水平位移最大差值分别为3 mm、7 mm、12 mm,实测值和模拟值均在监控量控制的±30 mm的范围内;对于管线的竖向位移而言,模拟结果和实测结果均显示管线位移变化幅度最大的点位于管线的中部,实测值略大于模拟值,两者数值分别为11.84 mm、7.90 mm,均满足小于20 mm的要求,模拟效果较为理想.

This paper takes the subway project of deep foundation pit engineering in Tianjin as a background and ana-lyzes the actual monitoring data of horizontal and vertical displacement of crown beam and vertical displacement of the surrounding pipeline during excavation of foundation pit.On its basis,three-dimensional analysis and calculation models are established by large-scale finite difference software FLAC-3D.By comparing the simulation results with the actual monitoring results,we can draw the conclusion that the numerical simulation results are in good agreement with the actual monitoring data.Under three conditions,the crowns show an upward displacement in the vertical direction,the trend of the simulation curve is more gentle and the measured curve of the ups and downs is more obvious,but there is not much differ-ence between the two.Three cases of the difference between the two are3.5mm,4.0mm and5.0mm or so.The analog value and the field monitoring value are within25mm of monitoring and control value.The maximum difference of the horizontal displacement of the crown beam is3mm,7mm and12mm respectively.Measured values and analog values are within±30mm of monitored quantity control.In terms of the vertical displacement of the pipeline,both the simulation results and the measured results show that the maximum point of change in the displacement of the pipeline is located in the middle of the pipeline.Measured values are slightly larger than analog values,these two values are11.84mm and7.90mm respec-tively,both of which meet the requirements of less than20mm,and the simulation results are satisfying.