Low-carbon effects of constructing a prefabricated subway station with temporary internal supports: An innovative case of Shenzhen, China

The traditional cast-in-site (CIS) construction method for subway stations has presented significant challenges to the construction industry in light of the growing labor shortage, prefabricated technology represents a promising alternative. This study introduces a novel prefabricated subway station structure, characterized by the innovative features of "Internal support + Large components + Full assembly." Additionally, the technical processes of the newly designed temporary internal support system for the case station are presented in detail. A greenhouse gas (GHG) emissions quantification model based on construction decomposition is established using the life cycle assessment (LCA) method to assess the low-carbon effect of constructing prefabricated subway stations. Moreover, an integrated project quota GHG emissions inventory is created. The findings demonstrate that the GHG emissions of the full-assembled structure, per unit area, are 6.55% lower than those of the CIS structure, resulting in an emission reduction benefit of 11.21 t CO2e. Notably, structural optimization and reduced material loss rates contribute to an 8.47% decrease in embodied emissions of materials. On average, the GHG emission intensity of the full-assembled station structure during transportation and on-site assembly is higher than that of the CIS structure, amounting to 4.48 t CO2e for a single ring-structure. Regarding GHG emissions during construction, the main structure and the exterior-protected structure of the case station account for 53.62% and 39.24% of the total emissions, respectively. Compared to prefabricated subway station using the temporary anchor cable supporting structure, the temporary internal support system could avoid unnecessary occupation of underground space, which is vital for the sustainable development of underground space in big cities.