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Objective As the development and utilization of urban underground space advances towards the three-dimensional and multi-dimensional direction, there are more and more over-crossing and under-crossing urban rail transit projects. Among them, the close under-crossing construction of new stations with large cross-section has a significant impact on the surrounding environment. Therefore, it is urgent to carry out an in-depth study on the ground settlement and deformation law of existing stations during the new station construction process closely under-crossing existing stations by Pile-Beam-Arch (PBA) method. Method Based on the actual engineering case of Beijing Metro Line 6 Pinguoyuan Station, which closely under-crosses the existing station with same name on Metro Line 1, the law of ground settlement and deformation of the existing station is analyzed by adopting numerical simulation method in the study. By comparing the actual monitoring data, the actual situation of ground settlement and deformation of the existing station during the construction process is further verified, and the numerical simulation results are compared and analyzed with the measured data. Result & Conclusion The most unfavorable stages for ground settlement and existing structure deformation are the guide hole excavation stage and the second lining arch stage of PBA method. After the completion of second lining arch construction, both the ground settlement and the deformation of the existing structure show rebound phenomenon. In addition, the stiffness of the existing station has a significant inhibiting effect on the ground settlement above, which is manifested in the fact that the ground settlement value of the overlapping section is smaller than that of the non-overlapping section. The deformation of the existing station structure caused by new station constructed with PBA method is mainly the rigid body displacement, while it caused track structure deformation is mainly the overturning deformation, which is locally manifested as rigid body displacement.

Objective A new station constructed with PBA method closely undercrossing existing station will influence the deformation of the latter′s structure. The influence law needs to be studied. Method Based on the project of Pingguoyuan Station on Beijing Metro Line 6 closely undercrossing the existing station, a finite element model is established by the GTS NX finite element analysis software, and its computing accuracy is verified through comparison with the actual monitored results. According to the calculation results of the finite element model, the impact of PBA (pile beam arch) method construction on the existing station is studied, and the influence of the existing station on land subsidence is analyzed. Result & Conclusion In the process of PBA construction, the construction stages that greatly affect the track structure and the building structure of the existing station are the guiding hole excavation and the second lining arch stages. The closer the construction is to the existing station, the smaller the land subsidence. When the monitoring sections are at the same location, the larger the existing station structure section, the smaller the land subsidence. With the same section size of the existing station, the closer to the excavation centerline of the new station, the greater the land subsidence value. The influence range of the existing station is related to the sectional size of the existing station structure.

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