LIFE-CYCLE CARBON FOOTPRINT OF UNDERGROUND INFRASTRUCTURE

The construction industry is a major source of greenhouse emissions, and underground infrastructure, including tunnels, is responsible for a significant proportion of the overall carbon emissions. Studies on the carbon footprint of tunnels often focus on only part of the full life cycle or on a particular type of tunnels only, and do not consider and compare the carbon emissions of different types of tunnels over the full life cycle. This paper compares the carbon footprint of the four common types of tunnels, namely, shield tunnels, new Austrian tunnelling method (NATM) tunnels, cut-and-cover tunnels, and immersed tunnels, during the design, construction, operation and maintenance (O&M), as well as dismantling phases. A case study of a real-world tunnel project is used to quantify carbon emissions and reveal differences in emission magnitude and distribution across tunnel types and life cycle stages. Finally, this paper suggests several key carbon reduction measures for achieving a low-carbon design.