The accurate accounting and effective management of carbon emissions in the embodied stage of railway tunnels are essential. Therefore, in this study, the process analysis method is used as the foundation for carbon emission accounting, and the input-output method supplements materials with unclear carbon emission coefficients. This results in the application of a hybrid approach to carbon emission accounting in the embodied stage of tunnels. The tunnels are divided into unit modules based on their functional differences, and a carbon emission accounting model for the embodied stage of railway tunnels is developed using the modularization theory. Furthermore, the data quality index is integrated with the Monte Carlo method to analyze the uncertainty in the inventory data for carbon emission accounting. Finally, the K-means algorithm is applied to classify the construction process into five management item categories, thereby establishing a targeted carbon emission accounting model based on carbon emissions and uncertainty. The results reveal the following: (1) The total carbon emission per linear meter of the tunnel is 11.625 t, with a variation coefficient of 6.13%. This confirms the reliability of the accounting results. (2) The carbon emission from secondary lining, primary support, and advance support accounts for 78.54% of the total emissions. Thus, the emissions fall under the people-materials-machines management category and should be prioritized in carbon emission management. (3) Furthermore, a detailed analysis of the carbon emissions and material uncertainty indicates that key materials in emission management should also be considered in addition to cement and steel, sand and stone, water-reducing agents, and slag powder. © 2025 Editorial Office of Tunnel Construction. All rights reserved.
