Dynamics-based economic and environmental benefits of excavated soil utilization along metro line: A case study

Abstract

This study focuses on the dynamic assessment of economic and environmental implications of repurposing excavated soil in urban metro construction projects. A system dynamics (SD) model was developed to analyze the excavation process stages, including generation, sorting, transportation, disposal, and utilization. By examining Xuzhou Metro Line 4 as a case study, the research assessed the economic advantages and greenhouse gas (GHG) emissions associated with reusing excavated soil. Results indicated that sorting efficiency significantly impacted GHG emissions; emissions decreased by 53% and the economic benefits are doubled when efficiency exceeded 30%. The use of a specific chemical agent (PG agent) reduced GHG emissions by 2,785 tons compared to cement, while increasing economic benefits by 39% at 20% content. The physical properties of excavated soil, particularly its particle distribution and plasticity, were found to influence both GHG emissions and economic benefits. Excavated soil with a lower plastic index provide a 9% increase in economic benefits and reduce GHG emissions by 14,636 t compared to excavated material with a plastic index of 70%. Mixing coarse particles into stabilized slurry soil on-site is recommended to optimize GHG emissions reduction and economic benefits. An optimal mixing ratio of 60% coarse particles for Xuzhou Metro Line 4 could lead to a reduction of up to 6,442 tons in GHG emissions with a slight increase in economic benefits. These findings offer valuable insights for enhancing economic benefits and reducing GHG emissions in metro construction through excavated soil reuse.

Keywords

• Dynamic assessment
• SD
• Excavated soil
• Economic and environmental benefits
• Metro line