Optimization of PBA Method Station Arch Support Scheme

［Objective］In PBA (pile-beam-arch) method construction, the choice of different arch support schemes significantly impacts the structural mechanics. To ensure the reliability and safety of urban underground structures, it is essential to rigorously monitor the land subsidence. Thus, it is necessary to systematically study the impact law of various arch support schemes on supporting structures and ground deformation. ［Method］Based on Tianhe East Station project on Guangzhou Metro Line 11 and using MIDAS/GTS software, a three-dimensional finite element model is constructed to analyze the land subsidence characteristics and the arch initial support internal force distribution law of various arch support schemes in depth. Meanwhile, field monitoring data of land subsidence is also used to validate the numerical simulation results. ［Result & Conclusion］The calculation results of initial support arches reveal that, compared to the CD (center diaphragm) method, the stepped method results in increases of 6.80% in land subsidence, 9.74% in initial support bending moment, and 14.62% in axial force, all meeting the construction control requirements. Research results of secondary lining arch support show that the alternating support removal method significantly reduces land subsidence with a smaller impact on arch initial support internal forces compared to the sequential support removal method. The scheme of combining CD method for initial arch support with alternating support removal method for secondary lining arch support proves to be advantageous.