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老城区改扩建工程具有地下管线、设施等障碍物较多,场地狭窄、基坑周边建筑物距离过近的特征,基坑支护设计难度大。为解决狭小空间基坑支护难题,以北京东长安街边全国妇联办公楼改扩建工程为例,借鉴了合理利用既有结构为基坑支护服务的设计理念,提出了新护坡桩与原有建筑物钢筋混凝土外墙形成台阶式支护体系和建立新老护坡桩联合支护体系的支护设计方案,并采用MIDAS GTS NX有限元数值软件对基坑沉降进行数值仿真模拟分析。数值分析和现场监测结果表明:(1)采用上述设计方案,基坑位移值远小于设计规范值,有利于工程的安全和稳定;(2)有限元数值模拟结果与现场监测结果吻合较好,通过有限元计算成果可更加全面地分析基坑支护系统各个部位的力学响应特征。研究成果可以对类似工程项目基坑支护设计方案选择提供参考。
The renovation and expansion project in the old urban area has many problems such as underground pipelines and facilities, narrow space, and buildings with too close distances. Therefore, it is very difficult to design the foundation pit support. In order to solve the problem of foundation pit supporting in small space, taking the reconstruction and expansion project of Beijing Women’s Federation as an example, this paper draws lessons from the design concept of rational use of existing structure as foundation pit supporting service, A reinforced concrete external wall is used to form a stepped support system and a support design scheme for the joint support system of new and old slope retaining piles. The numerical simulation of foundation pit settlement is carried out by using MIDAS GTS NX finite element software. Numerical analysis and field monitoring results show that: (1) With the above design scheme, the displacement value of foundation pit is much smaller than the design specification value, which is in favor of the safety and stability of the project. (2) The numerical simulation results of FEM are in good agreement with the on- Through the finite element calculation results, the mechanical response characteristics of various parts of the foundation pit supporting system can be analyzed more comprehensively. The research results can provide a reference for the design alternatives of foundation pit support for similar projects.