ABSTRACT
The growing emphasis on sustainability in infrastructure projects requires a comprehensive assessment of the carbon footprint associated with different construction methods. The aim of this study is to assess the carbon impact specifically associated with large diameter (>6m) tunnel construction using a Slurry Pressure Balance Machine (SPB) or a Variable Density Boring Machine (VD)
The primary objective is to determine the most realistic assumptions based on feedback from numerous projects, mainly in France, as well as consultations with companies and experts in the sector. Data on tunnel boring machines (TBMs) comes from AFTES (Association Française des Tunneliers et de l'Espace Souterrain) data sheets and from various other projects in France and around the world.
It should be noted that, at present, the current solutions available on the market are not capable of comprehensively assessing the carbon footprint of tunnel construction using TBMs. The methodology applied used EN 17472 standard and sensitivity analyses were conducted to determine the impact of different operational parameters. A specific database of primary emission factors (A0-A3) has been established to fit the specificities of tunnelling. A detailed life cycle assessment (LCA) encompassing the fabrication, transport, and use of the TBM, as well as the slurry treatment plant has been conducted, it also includes the manufacturing, transport, and implementation of lining segments, grout production, tunnel backfill, and the management of excavated materials.
This approach aims to offer aggregated emission factors to assess tunnel construction at early stage and solutions to reduce the carbon footprint of mechanized tunnels projects.
In addition, it emphasizes the need to consider site-specific factors when recommending excavation methods.
