地铁深基坑分区开挖监测及数值模拟

对于狭长的地铁车站深基坑,围护结构区域内岩土体在实际施工时经常采用分区的方式进行开挖。为了分析分区开挖工况下深基坑的稳定性规律,选取合肥市某地铁车站深基坑作为研究对象,运用有限差分软件对实际工程进行数值模拟。比较模型计算结果与现场实测结果,得到了基坑分区开挖过程中围护结构侧向位移、横向支撑轴力,以及地表沉降的变化规律。研究结果表明:现场实测结果与数值模拟结果较为接近且均小于规范限值,数值模型能较好地反映基坑变形特性;随着开挖的进行,围护结构变形出现明显的"鼓肚"状,最大侧向位移点向基坑中段移动;支撑轴力前期发展较快,之后趋于平稳;邻近地表沉降呈现为凹槽状,基坑开挖影响范围约在40 m内。研究结果可为其他类似工程设计或施工决策提供参考。

Partition Excavation of a Subway Deep Foundation Pit: Monitoring and Numerical Simulation

In practical engineering,rock mass in the long and narrow deep foundation pit of subway station is usually excavated in partitions.To obtain the stability rules of deep foundation pit excavated in partitions,finite difference software was adopted for numerical simulation.The deep foundation pit of a subway station in Hefei was taken as a case study.Through comparison between model results and field measurement results,the variation rules of retaining structure's lateral displacement and lateral support axial force and ground surface settlement during partition excavation were obtained.Results show that 1) field measurement results are in agreement with numerical simulation results,both within standard limits,indicating that the numerical model could well reflect the deformation characteristics of the foundation pit;2) with the proceeding of excavation,the "belly" of retaining structure bulged apparently,with the maximum displacement point moving towards the middle of the foundation pit;3) axial force of support developed rapidly in the early stage,and then tended to be stable;4) the adjacent ground surface settlement was in a groove shape,and the range within 40 m was affected by foundation pit excavation.The results could be taken as reference for the design and construction of similar projects.