地铁车站深基坑围护结构设计及其稳定性分析是地铁建设中的关键课题之一，开展西安地铁深基坑变形规律理论与监测的研究对指导西北地区深基坑信息化施工具有重要价值。本文以南门车站深基坑工程为背景，采用理论分析、现场监测和数值模拟相结合的方法，对西安地铁车站深基坑变形规律进行了研究，主要内容和结论如下： （1）分析了地铁车站深基坑变形的主要影响因素，研究了深基坑的变形机理及围护结构的破坏模式。研究表明，水文地质条件、基坑规模及土压力值、设计方案、施工方法与组织的合理性以及基坑渗流对深基坑变形影响较大；深基坑的变形主要包括三个部分：墙体变形、基坑底部隆起和周围地表沉降；破坏模式主要有弓形变形模式、深埋式变形模式、前倾型变形模式、踢脚型变形模式四种。 （2）完成了深基坑不同围护方案的比较与选型论证，给出了地铁南门车站深基坑围护结构的设计方案，并重点对围护桩和钢支撑进行了初步设计。 （3）制定了深基坑施工监测方案，并完成了现场监测工作。着重分析了围护桩的变形、钢支撑轴力变化和基坑周围地表沉降的规律。结果表明，桩体位移是围护结构变形特性的直接反映，而钢支撑对基坑变形有明显的限制作用。分析显示，围护结构设计方案基本合理，监测方案可行。 （4）运用FLAC3D软件对深基坑开挖过程进行了三维仿真模拟，给出了五种开挖工况下基坑位移、桩体侧移和基坑周围地表沉降的规律，计算结果和监测结果比较吻合；同时分析了西安地区黄土湿陷性对深基坑变形的影响，结果表明，随着黄土粘聚力增大，基坑变形量有所减小。

Design of the retaining structure and stability analysis of deep excavation in metro station is one of the key issues in metro construction. The study on the theory of deformation laws and monitoring of deep excavation in metro station in Xi’an has great significance to guide informational construction in deep excavation in northwest. In this paper, it uses the method that combines with the theoretical analysis, in-situ monitoring and numerical simulation followed the background of deep excavation of South Gate metro station. The main jobs are as follows: (1) The main factors affecting the deformation of deep excavation are analyzed, and the deformation principles and failure modes of retaining structure are studied. The research shows that the hydro geological conditions, the foundation size and earth pressure, design decision, the rationality of the construction methods and organization, and the pit seepage greatly impact the deformation of deep excavation. The deformation of deep excavation consists of three parts: the wall deformation, the bottom heave of the pit and the Surrounding ground settlement. The failure pattern of deep excavation contains the bow-shaped deformation mode, the buried-type deformation mode, the forward-type deformation mode, and the kick-type deformation mode. (2) The comparison of different support programs and the selection argument is completed. It proposes the design program of retaining structure of deep excavation of South Gate metro station, and gives the preliminary design focus on supporting pile and steel support selectively. (3) It designes the in-situ monitoring plan of deformation, and accomplishes the in-situ monitoring work. At the same time, it focuses on deep analysis of the horizontal deformation of the retaining piles, the axial force of steel support, ground settlement around foundation. The results show that displacement of pile is a direct reflection of deformation of the retaining structure, while the steel support of the foundation significantly limiting deformation. The analysis tells that the design program of retaining structure is basically rational and monitoring is feasible. (4) By the use of the software FLAC3D, a three-dimensional simulation of the entire process of excavation is accomplished, and the discipline of the displacement of the excavation and pile and the ground settlement around foundation is given under five cases. It indicates that the calculated results are identical with the measured ones. Also, the impact on the loess collapsibility of the deformation of deep excavation in Xi’an is analyzed. The results show that pit deformation decreases along with the cohesion increases.