基坑开挖对下方既有地铁隧道的影响分析和监测

Analysis and Monitoring of Foundation Pit Excavation in Existing Metro Tunnels

随着城市发展和地下空间的开发,越来越多的基坑工程横跨在既有地铁隧道的上方,基坑开挖卸荷将改变下方地铁隧道的应力场,使其产生不均匀的回弹变形和附加应力,从而对其安全稳定构成威胁。结合天津西站交通枢纽工程,研究基坑开挖卸荷对土体物理力学指标的影响,建立了一种卸荷土体特性下的有限元模拟计算方法,并应用"电水平尺"沉降自动监测系统对地铁隧道道床进行监测。研究结果表明,两者数据匹配性较好,能够相互验证,实现了地铁运营期间智能化、信息化监测的目的。

With urban development and underground construction in cities,more and more foundation pit projects are built right above the existing subway tunnels,which will change the stress field of subway tunnels and trigger the uneven springback deformation and extra-stress,threatening the safety of tunnels.Based on foundation pit engineering of the traffic hinge at Tianjin West Railway Station,a finit element simulation algorithm for the foundation pit project is adopted under the effect of lateral unloading on shear strength of the soil.During the excavation of the foundation pit,EL（electric levelling）beam automatic monitoring of settlement is also applied.The result of simulation analysis shows that the data of both methods have good matching,and realize the intelligent,automatic and informational monitoring purposes.