Embodied carbon assessment on road tunnels using integrated digital model: Methodology and case-study insights

Abstract

With the constant increasing road tunnel construction in China, embodied carbon emissions of tunnels play an important role in addressing the issue of the low-carbon construction. This study determined the carbon emission boundary based on the characteristics of road tunnels and proposed a digital model based framework for evaluating embodied carbon emissions in road tunnels, thus realizing the rapid calculation and visualization of tunnel carbon emissions. Through two typical region cases of road tunnels in different regions, the usability and universality of this framework are verified. Based on the carbon emission calculation results of the tunnels, a systematic analysis was conducted on the proportion of carbon emissions in each stage of the tunnel and the carbon emission characteristics of the whole construction process. The results show that the material production stage of road tunnel has the largest carbon emissions proportion, accounting for about 79%-87%, among which the carbon emissions contribution of concrete is the highest, followed by steel. Concrete and steel together account for about 90% of carbon emissions during the tunnel material production stage. The carbon emissions of road tunnel increase with the deterioration of the surrounding rock. The embodied carbon in the secondary support step of road tunnel contributes the most to the total embodied carbon, and the carbon emissions difference of different tunnels is mainly reflected in the two steps of primary support and secondary support of road tunnel. The visual presentation of embodied carbon in road tunnel by digital model can help to achieve the purpose of reducing carbon emissions in tunnels.