填海区临地铁超大直径圆环撑基坑变形控制及监测分析

填海区由于软土较厚，在填海区开挖基坑风险较大，若开挖基坑同时临近地铁隧道则还必须严格控制基坑开挖对临近地铁隧道产生的变形影响，因此在填海区位于地铁安保区内开挖基坑对变形控制要求极高。详细介绍了深圳填海地区、地铁安保区内某超大直径圆环撑软土深基坑变形控制技术，通过理论计算和三维有限元计算进行了详细分析，并与第三方实际监测结果作了对比分析，对类似工程具有参考及指导意义。得出如下结论：(1)支护结构的最大变形随着基坑开挖深度的增加而逐步增大，基坑开挖至坑底后，整体变形最大位置位于基坑两侧长边中部采用圆环支撑部位。基坑开挖至坑底时，第一道支撑最大水平位移发生在大约基坑中部冠梁位置，第二道支撑最大水平位移发生在大约基坑西北侧冠梁位置。(2)咬合桩+刚度较大的超大直径环形钢筋砼撑结构应用于较差地质条件下的软土深基坑工程中时在变形控制及减小基坑工程对周边变形影响等方面均非常有效。(3)基坑开挖过程中，三种方式所反映出的支护结构水平位移的变化趋势基本相同，随着基坑向下不断开挖，支护结构的最大水平位移量逐渐增加，但变化幅度有一定的差异。

Deformation control and monitoring analysis of super large diameter ring bracing foundation pit in reclamation area near metro area

. Due to the thick soft soil in the reclamation area, the risk of excavation of foundation pit in the reclamation area was high. If the excavation of foundation pit was close to the subway tunnel, the deformation impact of the excavation of foundation pit on the adjacent subway tunnel must be strictly controlled. Therefore, the excavation of foundation pit in the reclamation area was located in the subway security area, which was required high deformation control. The deformation control technology of a super large diameter ring bracing soft soil deep foundation pit in Shenzhen reclamation area and metro security area was introduced in detail in this paper. Through theoretical calculation and three-dimensional finite element calculation, which was compared with the actual monitoring results of the third party. which could be reference and guide significance for similar projects. The conclusions were as follows: (1) the maximum deformation of the supporting structure increased gradually with the increase of the excavation depth of the foundation pit. After the foundation pit was excavated to the bottom of the pit, the maximum position of the overall deformation was located in the middle of the long sides of the foundation pit, where the ring support was used. When the foundation pit was excavated to the bottom of the pit, the maximum horizontal displacement of the first support occurred at about the crown beam in the middle of the pit, and the maximum horizontal displacement of the