Mechanical response of a shield tunnel to normal fault displacement considering longitudinal bolt–segment interaction

In seismically active regions, shield tunnels crossing active faults may experience highly complex mechanical responses due to the combined action of segmental linings and bolted joints. However, the interaction between segments and bolts has often been neglected or oversimplified in previous studies, limiting the reliable evaluation of tunnel behaviour under fault dislocation. In this study, a three-dimensional finite element model is established for the Qingdao Jiaozhou Bay Second Submarine Tunnel. The central tunnel section is discretized into 30 lining rings connected by longitudinal bolts, which are explicitly represented by solid elements. The threaded and unthreaded bolt-hole interfaces are modelled using different interaction schemes to better capture the local contact behaviour. The results show that compressive soil-tunnel interaction stresses near the fault-tunnel intersection overlap longitudinally, giving rise to a distinct compaction effect. Joint opening is quantified in the longitudinal (Δ U ), vertical (Δ V ), and transverse (Δ W ) directions, while bolt-segment interaction is classified into shear, tension, and compression modes. Compression-induced opening and the corresponding bolt-segment interaction are found to dominate the overall mechanical response. Compared with conventional approaches, the proposed model better captures bolt-segment interaction, especially the shear resistance provided by bolts. These findings provide a refined numerical basis for the seismic design and safety assessment of shield tunnels crossing normal active fault zones.