地铁隧道盾构掘进对上跨地道基坑稳定性影响研究

Research on the Impact of Subway Shield Tunnelling on the Stability of Overcrossing Underpass Foundation Pit

地铁隧道盾构掘进对上跨基坑变形稳定特性和施工安全控制有着显著影响。文章依托呼和浩特市在建地道与在建地铁2号线"十"字交叉工程,通过数值模拟和实测监控对比分析,研究地铁隧道盾构掘进过程对上跨地道基坑稳定性影响规律。结果表明:受地铁下穿影响,基坑围护墙发生沉降和向基坑内侧变形,钢支撑轴力变化较小,主要以沉降变形为主,未加固时最终沉降累计值达16 mm;基坑下土体加固可显著减小基坑支护结构变形,沉降值可减少为未加固时的30%。有限元建模数值分析能够反映地铁下穿对基坑支护结构变形影响的一般规律,可为基坑围护结构的设计提供一定的理论依据。

The subway shield tunnelling has a significant impact on the deformation stability and construction safe⁃ty of the foundation pit of the overpassing underpass.Based on the intersection project between the under-construc⁃tion underpass and the under-construction Metro Line 2 in Hohhot,this paper studies the impact of subway tunnel shield tunnelling on the stability of overpassing underpass foundation pit through the comparative analysis of numeri⁃cal simulation and actual measurement and monitoring data.The results show that the retaining wall of the founda⁃tion pit is affected by the under-passing construction of the subway tunnel,resulting in settlement and deformation to the inner side of the foundation pit,and the change in the axial force of the steel strut is limited,mainly in the form of settlement,with the accumulative final settlement at about 16 mm under no reinforcement condition;the soil reinforcement under the pit can significantly reduce the deformation of the foundation pit support structure,and in particular,the settlement value can be reduced to 30%of that under no reinforcement condition.The numerical analy⁃sis by finite element modeling can reflect the general law of the effect of the under-passing subway tunnel construc⁃tion on the deformation of the foundation pit support structure,which can provide a certain theoretical basis for the design of retaining walls of foundation pits.