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围护结构的内力变形是基坑分析的主要内容,也是基坑工程安全控制的主要指标。目前基坑工程中对围护结构的监测侧重于位移测试,内力测试方法则不够准确。风险预警多以位移增量作控制指标,未能反映结构受力变形的真实状态。本文根据结构受弯时内力与变形的力学关系,提出了基于位移测试结果计算结构弯矩的方法——单元挠度法,并结合实例分析了单元长度的合理取值。结合基坑围护结构位移测试结果和由此计算得到的弯矩分析,考虑构件位移和内力两种控制参数,可对其风险状态进行综合判断。实例应用分析表明,所提出的围护结构综合风险判别方法计算简便,能动态得到即时弯矩和风险状态,并可弥补位移单参数风险预警的不足。
The internal force deformation of the retaining structure is the main content of foundation pit analysis and also the main index of the safety control of foundation pit engineering. At present, the monitoring of envelope structures in foundation pit engineering focuses on the displacement test, but the internal force test method is not accurate enough. Risk warning mostly uses displacement increment as control index, failing to reflect the true state of structural stress and deformation. According to the mechanical relationship between the internal force and the deformation when the structure is bent, a method to calculate the structural moment based on the displacement test is proposed, which is the unit deflection method. The reasonable value of the unit length is analyzed with examples. Combined with the displacement test results of the foundation pit retaining structure and the calculated bending moment analysis, considering the control parameters of component displacement and internal force, the risk status can be judged synthetically. The example application analysis shows that the proposed comprehensive risk identification method of envelope is simple and easy to calculate, which can get instantaneous moment and risk status dynamically and make up for the shortcoming of single parameter risk warning of displacement.