Longitudinal structural vulnerability analysis of shield tunnels under adjacent excavation disturbances

• A longitudinal vulnerability-based method is proposed to assess shield tunnel safety under adjacent foundation pit excavation, incorporating geological uncertainties via random field theory. • The maximum longitudinal deformation is identified as the most effective control index for ensuring tunnel usability and safety, compared with circumferential opening and bending moment. • Tunnel vulnerability decreases nonlinearly with increasing tunnel and subgrade stiffness, with subgrade stiffness having a more pronounced effect. • Active reinforcement of the substratum is more effective in reducing failure risk than passive reinforcement of the tunnel structure.