Resilience-based design for subway shield tunnels in soft soils: a perspective from the tunnel–soil system

Abstract With the rapid expansion of metro networks in China, the cumulative length of shield tunnels constructed in soft soil has exceeded 6000 km. While extensive engineering experience has been accumulated, these tunnels are still increasingly affected by service-related issues, such as long-term settlement, deformation, structural damage, and water leakage. These defects impose challenges to both operational safety and maintenance costs. This study provides a systematic overview of the major defect types and their spatial distribution patterns, highlighting their implications for the resilience and safety of shield tunnels. The coupled development and interaction of these defects are analyzed, and the limitations of existing research methodologies are critically examined. Based on these findings, this paper introduced a novel load mode to consider service tunnel’s environmental load variations, thereby proposing insights for enhancing the resilience of shield tunnel design from the tunnel–soil interaction perspective. Meantime, an elastic–plastic resistance model is also developed to address the degradation of lateral resistance at the tunnel waist caused by the fluidity of soft soils. A mathematical formulation of system stiffness is further developed by treating the tunnel and soil as an integrated system. Building upon this formulation, a resilience‑based design method is proposed to ensure the resilient performance of shield tunnels throughout the entire life cycle. The method is validated through its application to the Foshan and Shaoxing metro systems, with results demonstrating that optimizing system stiffness can significantly improve the resilience of shield tunnel structures in soft soils.