深基坑开挖对邻近既有地铁隧道影响规律研究

发布时间：2018-07-23 09:19

【摘要】：随着城市建设的快速发展,为了满足居民日常出行的方便,在一、二线城市的人群聚集中心,地下空间的开发利用变得越来越普遍,由此在城市中心出现了大量深基坑工程。而这类基坑工程在施工过程中往往会对周围既有的建筑物、地下管线以及邻近的地铁隧道产生影响。因此,如何在深基坑的设计和施工中准确地计算土体和地铁隧道的水平和竖向位移,保证基坑本身和支护结构的安全以及临近建筑物和地铁隧道的安全和正常使用,是基坑施工中急需解决的问题。本文结合西安国际中心DK-2二期深基坑工程,采用ANSYS有限元软件建立了开挖基坑的三维有限元模型,定量地分析了在基坑开挖过程中,基坑围护结构的变形、基坑底部土体的隆起量、周围土体的沉降以及邻近既有地铁隧道的水平位移和竖向位移;研究了地铁隧道不同埋深、隧道与基坑不同水平间距、隧道处在不同土质条件下等影响因素对邻近地铁隧道结构的水平位移和竖向位移影响规律。主要结论如下:(1)基坑开挖初期,基坑两侧受到的土压力较小,对基坑围护结构的变形影响较小,随着基坑开挖深度的不断增大,基坑围护桩体的水平和竖向位移也不断增大,但竖向位移增大的幅度呈现出逐渐减小的趋势。(2)在基坑开挖过程中,随着基坑底以土体应力释放,基坑底部的土体隆起量也不断地增大,最大位移达到了28.8cm。(3)在开挖浅层土时,基坑周围土体的变形大致表现为线性变化,但随着开挖深度的增加,会出现一定的非线性变化。(4)基坑开挖过程中,隧道的变形主要以水平位移为主,且水平位移远大于竖向位移。(5)通过对地铁隧道的不同埋置深度进行模拟,结果表明:随着地铁埋置深度的不断增大,隧道的变形呈现出逐渐减小的趋势。当埋置深度小于20m时,隧道埋深的变化对隧道位移影响较大;超过20m时,影响较小。(6)通过对地铁隧道距基坑支护结构的不同水平距离进行模拟,结果表明7.5m是一个临界点。水平距离从7.5m增至10m的过程中,地铁隧道水平位移减小的幅度最大,达到了42.2%。而从10m增大到15m时,地铁隧道竖向位移的减小幅度达到了25.7%。
[Abstract]:With the rapid development of urban construction, in order to meet the convenience of daily travel of residents, the development and utilization of underground space become more and more common in the crowd gathering center in the first and second tier cities, so a large number of deep foundation pit projects appear in the city center. During the construction of this kind of foundation pit, the existing buildings, underground pipelines and adjacent subway tunnels will be affected. Therefore, how to accurately calculate the horizontal and vertical displacement of soil and subway tunnel in the design and construction of deep foundation pit, to ensure the safety of foundation pit itself and supporting structure, and the safety and normal use of adjacent buildings and subway tunnels, It is an urgent problem in foundation pit construction. In this paper, the 3D finite element model of the excavation foundation pit is established by using ANSYS finite element software combined with the DK-2 deep foundation pit project of Xi'an International Center, and the deformation of the retaining structure of the foundation pit during the excavation process is quantitatively analyzed. The uplift of the soil at the bottom of the foundation pit, the settlement of the surrounding soil and the horizontal and vertical displacement of the adjacent existing subway tunnel are studied, and the different horizontal distances between the tunnel and the foundation pit are studied. The horizontal and vertical displacement of the adjacent subway tunnel structure is affected by the influence factors of the tunnel under different soil conditions. The main conclusions are as follows: (1) at the beginning of foundation pit excavation, the earth pressure on both sides of the foundation pit is relatively small, and the deformation of the retaining structure of the foundation pit is less affected. With the increasing of the excavation depth, the horizontal and vertical displacement of the retaining pile body of the foundation pit is also increasing. However, the increasing amplitude of vertical displacement shows a decreasing trend. (2) during the excavation process, with the release of soil stress at the bottom of the foundation pit, the uplift of the soil at the bottom of the foundation pit increases continuously, and the maximum displacement reaches 28.8cm. (3) during the excavation of shallow soil, The deformation of soil around the foundation pit is approximately linear, but with the increase of excavation depth, there will be a certain nonlinear change. (4) during excavation, the deformation of tunnel is mainly horizontal displacement. And the horizontal displacement is far greater than the vertical displacement. (5) through the simulation of the different buried depth of the subway tunnel, the results show that the deformation of the tunnel gradually decreases with the increasing of the buried depth of the subway. When the buried depth is less than 20m, the variation of the buried depth has a great influence on the displacement of the tunnel, and when the depth is more than 20m, the influence is small. (6) through the simulation of the different horizontal distance between the subway tunnel and the supporting structure of foundation pit, the result shows that 7.5m is a critical point. In the process of increasing the horizontal distance from 7.5 m to 10 m, the amplitude of horizontal displacement of subway tunnel is the largest, reaching 42.2%. When the vertical displacement of subway tunnel increases from 10 m to 15 m, the reduction range of vertical displacement reaches 25.7m.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU753

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