为解决既有轨道交通地下结构与建筑规划更新需求不匹配引起的扩建或改造问题，结合不同的改造原因，总结既有地铁出入口改扩建结构设计关键技术重难点。以深圳市既有7号线黄木岗站B出入口改造设计为例，首先，从TOD（transitoriented development）站城一体化、消防及人防设计、运营组织、防涝能力、地面景观、结构工法、总工期和工程投资等角度对改造下沉广场方案进行总体论述；然后，对紧邻运营地铁出入口同深度基坑支护设计、未预留接驳条件的既有车站开门洞关键工序以及新旧混凝土连接节点构造等关键技术进行分析。研究表明： 1）对于既有运营地铁出入口改造方案应进行全专业综合充分论证，结合运营单位管理需求进行结构设计和施工组织设计，并做好防淹、防汛及应急预案。2）紧邻既有运营地铁出入口进行同深度基坑施工，可通过利用既有围护和预留反压土等措施，控制既有出入口和周边既有建筑物的变形，并应按照轨道交通运营安全保护区的相关要求对既有结构变形进行重点监测，信息化施工。3）对于未预留接驳条件且架设临时支撑条件受限的既有结构侧墙破除连通改造，可充分利用“时空效应”，采用楼板卸载和分段跳仓破除的方法； 新旧混凝土连接节点设计可采用新建梁柱结构与既有结构叠合的形式，并加强防水。

When the underground structures and buildings of rail transit do not match the renovation requirements, they should be expanded or even reconstructed. According to various reconstruction requirements, key technical difficulties in the design of the expansion and reconstruction of the existing metro entrance and exit are summarized. In this study, a case study is conducted on the reconstruction structure design of the entrance B of the Huangmugang station of the Shenzhen metro line 7. First, the overall construction of a sunken square is presented in terms of stationcity integration, fire protection design, operational organization, antiflooding capacity, landscape design, structural construction method, total duration, and investment of the transit oriented development(TOD) project. Then, the design of foundation pit support with the same depth of adjacent metro entrance, the existing station sidewall opening without reserved connection conditions, and the connection structure node of new and existing concrete are analyzed. The research results show the following: (1) Demonstration should be fully implemented before renovation, the structure and construction organization should be designed considering specific requirements, and antiflooding and emergency plan should be determined. (2) When constructing a foundation pit adjacent to the metro entrances and exits, the existing enclosure and reserve backpressure soil can be used to control the deformation of the entrances and exits and the surrounding buildings, and the structural deformation should be closely monitored, achieving informatized construction. (3) The floor unloading and sequential construction can be used to demolish the sidewall of the existing structure without reserved connection and temporary support conditions. Beam/column structures can be constructed to connect with the existing structure, and waterproof measures should be implemented.