Effect of fault dislocation on the deformation and damage behavior of ballastless track structures in tunnels

This study focuses on the mechanical behavior of slab track structures within railway tunnels that traverse fault zones. By combining the concrete damaged plasticity (CDP) model with the finite element method, a coupled simulation model of the slab track-tunnel-surrounding rock system has been established. The analysis primarily centers on the effects of fault dislocation on the stress, deformation, and damage characteristics of both CRTS II and CRTS III slab tracks, with the former featuring longitudinally connected track slabs and the latter characterized by unit-type track slabs. The results demonstrate that under normal fault dislocation, track irregularity, structural damage, and the interlayer gap all increase as fault displacement grows. Owing to its relatively higher structural stiffness, the CRTS II slab track is more susceptible to stress concentration, thereby leading to more severe damage to the track slab and base plate, as well as larger interlayer gaps. Specifically, the maximum damage variable of the track slab in the CRTS II slab track is 16 times that of the CRTS III slab track, and its maximum interlayer gap is 1.3 times larger than that of CRTS III slab track. By contrast, the unit-type design of the CRTS III slab track endows it with better adaptability to foundation deformation and mitigates stress concentration. However, this design leads to more increased track irregularity. The maximum upward bending deflection of the rail on the hanging wall side of the fault in the CRTS III slab track is twice as large as that of the CRTS II slab track. Under reverse fault dislocation, compared to normal fault dislocation, the compressive effects reduce structural damage, yet the trends of deformation and interlayer contact remain consistent with the variation of fault displacement. This research offers valuable insights for the design and maintenance of high-speed railway tracks within tunnels that cross fault zones.