为解决已建成运营的地铁与外部环境不协调和不能满足新的运营功能需求的问题，必要时需对运营地铁工程进行改扩建。以西安地铁已实施的几种土建相关改扩建工程（包括车站主体、车站出入口、车站风亭、车站小型附属构筑物）为例，对改扩建工程的背景、实施方案、实施效果、风险源及技术措施、运营保障措施、实施管理机制、投资及综合效益等方面进行分析和梳理。认为： 1）对地铁进行改扩建的方式是灵活多样的，应通过多角度比选出最佳改扩建方案； 2）实施前应充分论证和验算，将不利影响、实施风险、工程投资降到最低； 3）在乘客密集的公共区域施工作业，需加强运营管理，制定专项紧急保障方案，避免发生运营事故； 4）现缺少针对改扩建工程的施工及设计规范、标准，缺乏系统化的管理程序及机制，建议尽早形成地铁改扩建完善的建设程序、合理的管理机制。

In order to solve the problems such as inharmonious internal and external environment and backward facilities, rehabilitation and expansion should be carried out for operating metros. Several rehabilitation and expansion schemes related to civil work (including station main body, station entrance/ exit, station ventilation pavilion and small ancillary structures of the station) for Xi′ an metro stations are taken for examples to analyze and summarize the background, implementation, effect, risk sources, technical measures, operating measures, management mechanism, investment and comprehensive benefit of rehabilitation and expansion works. The conclusions are drawn as follows: (1) The schemes for rehabilitation and expansion of metro are various, hence, comparison and selection should be carried out. (2) Sufficient demonstration and checking before scheme implementation should be adopted to minimize the adverse impact, implement risk and project investment. (3) The operational management should be strengthened, and the specific emergency schemes should be made to avoid accidents when constructing in crowded public area. (4) It is short of specification and standard for construction and design of rehabilitation and expansion, as well as the systematic management procedure and mechanism. It is suggested that the optimum construction program and rational management mechanism should be determined as soon as possible.