基坑开挖对邻近既有盾构隧道的影响分析

为研究基坑开挖对既有盾构隧道产生的影响,以某已建地铁周边基坑工程为背景,通过数值模拟的方法对开挖过程中隧道的位移和膨胀变形进行研究,并与现场监测数据进行了对比分析。结果表明:基坑开挖时,两平行隧道中距离基坑较近隧道的位移变形量大于较远隧道的位移变形量; 同一隧道同一监测线上距离基坑越近隧道监测点位移总变形量越大,且隧道整体朝向基坑方向偏移; 同一隧道的同一竖向截面上不同点的位移不同,靠近基坑一侧监测点位移数值大于背向基坑侧的位移数值; 隧道在整体隆起变形趋势下,存在“竖鸭蛋”变形趋势; 纵向隆起位移量随监测点呈抛物线分布并向两边逐渐减小; 数值模拟结果与现场监测结果基本一致,验证了模拟的正确性; 研究成果可为因地铁周边新建建筑引起地铁变形可能发生的危害做出预警,并提出相应防治措施,为待建地铁隧道项目的安全设计和施工提供参考。

Analysis on Influence of Foundation Pit Excavation on Adjacent Shield Tunnel

In order to study the influence of foundation excavation on the existing shield tunnel, the displacement and expansion deformation of the tunnel during excavation were studied by numerical simulation method with the background of a foundation project around a existing metro line, and were compared and analyzed with the field monitoring data. The results show that during the foundation pit excavation, the displacement of the tunnel near the foundation pit is greater than that of the tunnel far away. In the same monitoring line of the same tunnel, the closer to the foundation pit, the greater the total displacement of the monitoring point, and the tunnel is shifted toward the pit as a whole. The displacement of different points on the same vertical section of the same tunnel is different, and the displacement values of the monitoring points on the side near the pit are larger than those on the back side of the pit. The tunnel has a tendency of “vertical duck-egg” deformation under the overall uplift deformation trend. The longitudinal uplift displacement is parabolically distributed with the monitoring points and gradually decreases to both sides. The numerical simulation results are basically consistent with the field monitoring results, which verifies the correctness of the law. The results of the study can provide early warning of the possible hazards of subway deformation caused by new buildings around the subway and propose corresponding prevention and control measures, and provide reference for the safe design and construction of the metro tunnel project to be built.