黄土地层基坑开挖对既有地铁隧道影响分析

Analysis on Influence of Excavation of Pit on Existing Metro Tunnel in Loess Layer

为解决黄土地区基坑开挖对近接地铁隧道运营安全带来的影响,研究基坑工程与地铁隧道之间的相互作用机理,基于正交试验分析了水平净距,竖直净距等影响因素敏感性程度,并进一步结合西安地铁八号线幸福林带基坑工程,采用室内模型试验分析了基坑开挖对既有隧道影响的受力变形规律,结果表明:基坑与隧道的竖直净距和水平净距对隧道水平和竖直位移影响显著;在施工过程中,隧道管片的拉伸值始终大于压缩值,且拉伸方向和水平内径变化规律相反;管片拱顶和右墙处弯矩逐渐增大,而拱底和左墙则呈现先减小后增大的趋势;管片周围土压力主要集中在拱底和右墙处,且一直保持减小趋势,其纵向土压力差不断减小,水平土压力差不断增大,导致隧道朝上和朝基坑方向移动。

In order to study the interaction mechanism between foundation pit engineering and adjacent tunnel engineering in loess area,the sensitivity degree of various factors was analyzed based on orthogonal test.Furthermore,based on the foundation pit engineering of Xingfu forest of Xi'an metro line 8,the indoor model test was used to analyze the stress and deformation law of the interaction between foundation pit and tunnel.The results show as follows.The vertical clear distance between foundation pit and tunnel during the construction process,the tensile value of the tunnel segment is always greater than the compression value,and the tensile direction and the horizontal inner diameter change in the opposite direction.The bending moment changes at the segment vault and right wall are positively correlated with the excavation steps,while the arch bottom and left wall first decrease and then increase.The earth pressure around the segment is mainly concentrated in the arch bottom and right wall.The vertical earth pressure difference decreases and the horizontal earth pressure difference increases,which leads to the tunnel moving upward and towards the foundation pit.