Optimization for temporary support unloading scheme and on-site monitoring of large-span column-free underground station

The newly-built Gangshabei comprehensive transportation hub station is an underground structure with three floors. The design of the 48 m × 52 m atrium of the station is completed without interior column. With complex types of structural components, multiple system transformations are involved in construction process. The unloading time of the temporary support, and how the unloading process would affect the stress state of the built structure are critical to the construction safety. Based on the original scheme, various temporary support unloading schemes were proposed. The influence of different unloading schemes on the structural stress state was compared through finite element simulation analysis. Unloading the temporary support after the erection of the steel girders on the first basement level is determined to be reasonable, which reduces the tensile stress of the concrete slab on the first basement level reduced by up to 14% compared to original plan. On this basis, to make the stress state of the steel girders on the first basement level change more smoothly, the “unloading-uplifting-secondary unloading” scheme was further proposed and applied to the actual structure. Field monitoring results show that earth covering load has the greatest impact on the structural stress state, then the secondary unloading. During the entire unloading process, the structural stress state changes smoothly, the optimized scheme is proved to be safe and effective. © 2023 Science Press. All rights reserved.