Shaking table tests on dynamic damage evolution mechanism of tunnel-slope system by seismic motions

The seismic coupling disaster effects of tunnels traversing slopes in strong earthquake zones, along with the dynamic damage evolution mechanism of the tunnel-slope system, remain key scientific challenges in the field of seismic resilience for underground engineering. In this study, a shaking table model test was conducted to simulate the dynamic response behavior of the tunnel portal section under seismic loading. Through a combined analytical approach utilizing the Hilbert-Huang Transform (HHT) and the Marginal Spectrum (MS), the mechanisms governing seismic energy transfer in the tunnel-slope system were clarified. The results indicate that the seismic deformation of the tunnel exhibits an alternating tensile-compressive cyclic pattern. In the near-slope region, uplift-type failure dominates, whereas in the far-slope region, the failure mode is characterized by compressive deformation progressing from the upper and lower sections of the tunnel toward its center. As the seismic intensity increases, the peak frequency of the tunnel exhibits a gradual decrease (from 16.18 Hz to 14.85 Hz). The MS amplitude is predominantly concentrated in the 10-30 Hz frequency band, with the lower regions, such as the tunnel invert and sidewalls, demonstrating significant damage sensitivity. As system damage progresses, the dynamic relationship between the tunnel and the slope undergoes continuous evolution, and the formation and transfixion of the sliding surface serve as a sufficient condition for slope instability. The damage evolution process of the tunnel-slope system can be categorized into four characteristic stages: initial microdeformation stage -* plastic damage incubation stage -* shear slip development stage -* collapse and sliding failure stage. The research findings provide significant guidance for the seismic design of tunnel engineering in strong earthquake zones and the assessment of slope stability.