Seismic dynamic response analysis for tunnels considering coseismic displacement

Fault dislocation is a form of dynamic impact load that induces permanent deformation of the stratum in the vicinity of the fault. Based on the finite-fault source and crustal velocity model, coseismic displacement is computed according to the layered dislocation theory. Then, this paper presents a fling-step effect ground motion expression considering the pulse period, peak displacement and permanent displacement. According to the fling-step effect ground motion expression, the coseismic displacement field is transformed into a dynamic displacement process, and the seismic response of tunnels considering permanent displacement is analyzed. Taking the 2022 Menyuan earthquake as an example, the deformation and damage characteristics of the Daliang tunnel are analyzed, validating the rationality of the proposed method. Additionally, the impacts of pulse period and peak displacement of near-fault ground motions on seismic response analysis of crossing fault tunnel are investigated: shorter pulse periods correspond to larger unidirectional velocity pulse amplitudes, resulting in more pronounced impact effects of fault slip and more severe tunnel damage; at constant pulse period, higher peak displacements result in more severe tunnel damage, and the impact of displacement rebound on structural damage is not negligible; the destructive effect of peak displacements on tunnels is more pronounced compared to pulse periods of ground motions.