基坑施工对自身及既有地铁结构的影响分析

Influence of Foundation Pit Construction on Itself and Existing Subway

基坑施工会引起周围地层初始应力发生改变,造成基坑自身的变形,同时会导致紧邻的地铁结构受力和变形发生改变,严重时可能会对地铁运营的安全产生影响。因此,评估基坑工程对邻近地铁结构安全性的影响尤为重要。以某一地铁线路周边基坑工程的施工为例,采用大型有限元软件ABUQUS建立三维模型,模拟分析基坑施工对周边地铁结构位移变化情况,分析计算地铁结构的位移变化,以此来研究基坑施工对邻近既有地铁结构变形的影响。研究结果表明,基坑土方开挖导致土体自重应力释放,坑内土体产生回填变形,受围护结构内外侧水土压力差异的影响,导致基坑周边应力重新分布,地铁结构受应力变化的影响向基坑侧移动,出现最大位移位置为距离基坑最近处的基坑中部位置。通过对变形机理的分析,提出相应的控制措施,为今后的类似工程提供参考。

The foundation pit construction will cause the change of the initial stress in the surrounding strata, which causes the deformation of the foundation pit itself, and will also change the stress and deformation of the adjacent subway structure, which may affect the normal operation of the subway line seriously. Hence, it is important to assess the effect of the excavation of fundamental pit on the structure safety of adjacent tunnels. In this paper, by taking the existing subway lines in a nearby deep foundation pit in Tianjin as an example, the three-dimensional spatial entity model is established by the ABUQUS finite element numerical simulation analysis method. The construction process of the foundation pit adjacent to the subway structure is simulated and the deformation of the subway structure is analyzed and calculated to study the influence of the deformation of the adjacent existing subway structure. The results show that the soil mass in the pit is uplifted and the lateral soil of the enclosure moves to the foundation pit side, which leads to the displacement of the subway structure. The maximum displacement occurs in the position of the subway structure near the foundation pit and is located near the middle of the foundation pit. Through the analysis of deformation mechanism, the corresponding control measures are proposed to provide reference for similar projects in the future.