深软场地地铁车站深基坑开挖变形实测分析

研究目的:对某大型地铁车站深基坑开挖过程中的软弱场地变形监测结果进行了统计分析,对基坑开挖引起的地面沉降、墙体水平位移和立柱桩体沉降的时空变化规律进行了整体分析,尤其是对不同基坑开挖深度对基坑变形速度的影响规律进行了总结。相关的结论和建议对城市软弱地基内地铁车站深基坑的变形监测方案设计、施工组织设计和施工安全控制等都具有一定的参考价值和指导意义。研究结论:(1)在深软场地深基坑开挖完成后地铁车站主体结构施工过程中拆撑可能造成地面的沉降比基坑开挖过程中产生的累积沉降还要大,应加强地铁主体结构施工过程中地面的沉降观测;(2)基坑侧壁水平累积位移与每次开挖土层厚度及其土层性质关系密切,随着开挖土层埋深的增大,基坑侧壁水平累积位移累积速度明显加快;(3)当基坑开挖深度有较大差异和基坑底部土层厚度分布极不均匀时,应考虑验算立柱桩的差异沉降;(4)软弱场地深基坑工程开挖引起的场地变形时空效应非常明显,随着开挖的进行,应沿纵向按限定长度逐段开挖,在每个开挖段分层、分小段开挖。

Analysis of the Construction Deformation of the Foundation Pit Excavated for Metro Station Built in Soft Site

Research purposes:In this paper,the construction deformations of the foundation pit excavated for metro station built in soft site are counted in system.The settlement of the ground surface,the horizontal deformation of wall and the settlement of the upright column are analyzed based on the monitoring results.The conclusions and suggestions given in this paper can be referenced in design and construction of the similar foundation pit. Research conclusions:(1) The ground surface settlement during the underground structure being constructed may be larger greatly than that during the foundation pit being excavated when the underground structure is built in the soft site.Accordingly,the deformation of the foundation pit during the underground structure being constructed must be intensified.(2) The horizontal deformation of the support wall is very sensitive to the excavation thickness and the properties of soil layers every time.It is obviously that the cumulate horizontal displacement of the support wall becomes increasing faster with the excavated depth of foundation pit increasing.(3) When the excavated depth of foundation pit and the thickness of soil layers laying under the bottom of foundation pit change obviously,the differential settlement of upright column must be considered carefully.(4) The space-time variation of the foundation deformation is obviously when the soft soil layers existing around the foundation pit.The excavation size of soils must be designed carefully.