A stratigraphy-informed framework for GHG emission reduction and resource recovery in shield tunnel spoil management

Tunnel construction generates a substantial amount of construction and demolition waste (CDW), leading to significant greenhouse gas (GHG) emissions from waste management. This study develops a GHG emission assessment framework for sustainable management of slurry pressure balance (SPB) shield tunneling spoil, incorporating stratigraphic variability into the analysis. The framework integrates emission factors with particle conservation principles to quantify the carbon reduction potential of reusing excavated spoil under varying geological conditions. Laboratory experiments determined the reusable fine aggregate rates content for different spoil types, and six representative stratigraphic combinations were analyzed to validate the framework. Case study results showed that recycling fine aggregate as grouting materials and bentonite substitute increased GHG reduction benefits by 13.9%, avoiding a total of 902,990 kg CO 2 e over 219 tunnel rings. Additionally, emissions associated with the outbound transport and disposal of unrecycled coarse aggregates amount to 779,610 kg CO 2 e. These can be further mitigated through on-site reuse for non-sintered brick production, which reduces disposal-related emissions by 40.34% and generates economic benefits of CNY 131,456. These findings underscore the environmental and economic advantages of stratigraphy-adaptive spoil reuse strategies, supporting carbon neutrality and sustainable infrastructure development. • A stratigraphy-adaptive framework was proposed to quantify GHG reductions in SPB shield tunnel spoil recycling. • Stratigraphic variability-based reuse evaluation improved the accuracy of spoil recycling benefit estimation. • Optimized spoil reuse improved GHG reduction by 13.9%, while coarse spoil reuse cut disposal emissions by 40.3%.