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北京地铁9号线工程丰台东大街站,通过对现场围护结构的监测、分析发现:砂卵石地层随着基坑开挖变形实效性较快,基坑开挖期间变形明显,开挖完成后,变形立刻呈现收敛趋势;钢支撑架设初期,轴力会有所衰减,后期轴力随着开挖深度的增大而增大;地表沉降最大值应与桩体变形最大值存在一定的线性关系;平顶直墙形式暗挖结构段在土方开挖期间呈现整体下沉,中隔壁拆除时受力改变,变形呈抛物线形式,且土方开挖完成、中隔壁拆除期间的沉降量均占较大比重,甚至中隔壁拆除期间所占比重更大。
Through the monitoring and analysis of on-site enclosure structure, the analysis shows that the deformation of sand-gravel stratum is rapid with the excavation and deformation of the foundation pit, and the deformation during the excavation of the foundation pit is obvious. After excavation is completed , The deformation tends to converge immediately. At the initial stage of steel support erection, the axial force will be attenuated and the axial force increases with the excavation depth at the later stage. The maximum settlement of the ground surface should have a certain linear relationship with the maximum deformation of the pile ; The undercut structure segment in the form of flat top straight wall shows overall sinking during the earthwork excavation, the force is changed when the middle wall is demolished, the deformation is parabola, and the excavation of earthwork is completed, and the settlement during the removal of the middle wall occupies a larger proportion Proportion, even in the demolition of the wall during the larger share.