Qualitative evaluation of load components for cross-fault tunnels under fault stick–slip and seismic effects: Insights from dual-shaking table array tests

• The effects between fault stick-slip and seismic effect (FSS-SE) on tunnel structures were experimentally investigated using dual-shaking table array tests. • Load components of cross-fault tunnels under FSS-SE faults are qualitatively identified, including dislocation load, dynamic dislocation effect, and seismic load. • The fault stick-slip rate plays a critical role in governing deformation modes, highlighting the significance of dynamic effects. Conventional tunnel engineering designs have notable limitations in addressing the fault stick-slip and seismic effects (FSS-SE). To overcome the constraints of quasi-static fault-dislocation model tests, this study employs a dual-shaking table setup to impose non-uniform excitation. A controlled loading framework is established to combine a prescribed permanent fault dislocation with pulse-type near-fault ground motion. The validity of the fault stick-slip simulation is examined using the measured displacement histories of the model box, observed deformation, and failure characteristics of the surrounding rock. The response of a tunnel with flexible joints is analyzed in terms of deformation, damage patterns, acceleration, and strain. The results indicate that the most severe damage is concentrated in tunnel segments located within the fault fracture zone and moving block. The load components for tunnel structures under FSS-SE are conceptually decomposed into three interrelated components: dislocation load, dynamic dislocation effect, and seismic load. Fault dislocation provides the fundamental cause of tunnel damage, while the fault slip rate plays a critical role in governing deformation modes and failure characteristics. With increasing slip rate, the dynamic dislocation effect becomes more pronounced, driving the tunnel response from an overall bending-dominated pattern toward a combined bending-shear mode with increasingly prominent shear-type features. Seismic loading further aggravates damage, particularly for tunnels that have already been weakened by dislocation load and dynamic dislocation effect. The proposed framework helps clarify potential failure mechanisms of cross-fault tunnels and offers engineering insight for coordinated fault-resistance and seismic design.