地铁出入口原位扩建施工力学行为及关键技术研究

Research on Mechanical Behavior and Key Technology of In-situ Expansion of Metro Entrance and Exit

结合北京市轨道交通昌平线南延西土城站改造工程,以既有A出入口改造为研究背景,结合周边环境及地质情况进行方案比选,并对加固措施、破口改造节点、施工步序等关键技术进行优化研究。在此基础上,建立运营地铁出入口洞桩法原位扩建施工全过程三维有限元数值模型,并结合现场监测结果,探究扩建施工诱发的地表沉降与既有出入口结构变形的规律。结果表明:(1)洞桩法施工形成的桩梁拱承载体系可以保护主体结构施工作业的安全,承受地层荷载,有效减小地层沉降和环境影响,保证既有出入口结构的安全;(2)数值模拟结果与现场实测数据基本一致,其中,现场监测与数值模拟结果中,地表最大沉降分别为62.8 mm和65.07 mm,初支扣拱与二衬扣拱两阶段对地表沉降的贡献最大;(3)既有结构主要影响阶段为大开挖阶段,最大沉降为1.4 mm。研究成果可为运营出入口改扩建工程提供新的思路和方法。

Based on the renovation project of the Xitucheng Station on the Changping Line of Beijing Rail Transit,taking the existing A entrance and exit renovation case as the research background,a scheme comparison was conducted by combining the surrounding environment and geological conditions.Key technologies such as reinforcement measures,breakthrough renovation nodes,and construction steps were optimized and studied.Establish a three-dimensional finite element numerical model for the entire process of in-situ expansion construction using the subway entrance and exit pile method,and explore the laws of surface settlement induced by in-situ expansion construction using the subway entrance and exit pile method and the deformation of existing entrance and exit structures based on on-site monitoring results.The results show that:(1)using the hole pile method for construction,the pile beam arch bearing system formed by it can protect the safety of the main structure construction operation,bear the geological load,effectively reduce geological settlement and environmental impact,and ensure the safety of the existing entrance and exit structures;(2)The numerical simulation results are basically consistent with the on-site measured data,and the maximum surface settlement of the on-site monitoring and numerical simulation results are 62.8 mm and 65.07 mm,respectively.The initial support arch and the second lining arch have the greatest contribution to surface subsidence in the two stages;(3)The main impact stage of the existing structure is the large excavation stage,with a maximum settlement of 1.4 mm.The research results can provide new ideas and methods for the operation of entrance and exit renovation and expansion projects.