Abstract: The excavation and support of ultra-large-section underground storage tank space is challenging, the construction efficiency is low, and the construction period is short. To address these issues, a case study is conducted on an ultra-large-span underground storage tank project, and two construction plans and their corresponding detailed construction support processes and support parameters are proposed based on the characteristics and difficulties of the project. Through numerical simulations, the construction process of the tank body is simulated using the birth death element method and soft modulus method. Furthermore, the differences between the two construction plans are analyzed in terms of vertical displacement of surrounding rock, vertical stress of structure, and tension of anchor bolts and cables. After scheme comparison, it is confirmed that the strip reverse roof excavation method is employed for the subsequent tank body construction. Finally, based on the Platts theory and suspension theory, the layout of prestressed anchor cables is optimized, and the feasibility of the plan is verified through monitoring data and actual construction period. The results indicate that: (1) The proposed construction methods, annular reserved center rock column excavation method and the strip reverse roof excavation method, as well as the corresponding support scheme and parameters, effectively solve the problem of excavation and support in underground spaces with large-span and low-grade surrounding rocks. (2) Through numerical simulation and on-site monitoring verification, the strip reverse roof excavation method and related optimized anchor support scheme have good applicability to this project.

Key words: ultra-large-span underground storage tank, construction technology, construction plans, support parameters, optimization design