Dynamic response of high-steep rock slope-tunnel system with cataclastic rock belt under seismic-rainfall coupling: Shaking table test

The dynamic response of slope-tunnel systems under coupled seismic-rainfall exhibits pronounced nonlinearity and complex time-dependent behavior. Through large-scale shaking table model tests and coupled time-frequency analysis, the dynamic responses and failure mechanisms of high-steep rock slope-tunnel systems with cataclasite under coupled seismic-rainfall were systematically investigated. The results indicate that the rainfall and slope grade change points tend to induce localized dynamic amplification, while tunnel invert and cataclasite rock suppress acceleration amplification. With increasing seismic intensity, the peak ground acceleration (PGA) of the slope surface increases by up to 97.4% in the relative elevation range of 0.76-1.0. Whereas the natural frequency gradually decreases, with the dominant frequency shifting from 12.99-13.82 Hz to about 10.22 Hz. As the slope damage deformation intensifies, the modal deformation at the slope crest reaches approximately 4-5 times greater than that observed below the tunnel. The damage factor D exhibits an S-shaped evolution trend, with a sudden increase of 17.3%–17.9% at 0.2 g after rainfall. In slope-damaged regions, the strain localization zones gradually develop into interconnected failure bands, and the instantaneous damage coefficient ( F ) decays at the initial stage. Hilbert spectral energy becomes concentrated and shifts toward the dominant frequency (10 Hz), accompanied by attenuation of high-frequency components (>15 Hz). The marginal spectrum amplitude within the 0-4 Hz range tends to dissipate at relative elevations above the tunnel level. Meanwhile, the failure mode under coupled seismic-rainfall follows the sequence: tensile cracking at the slope crest, bending deformation within the cataclasite, propagation of the tensile crack, compressive deformation at the slope grade change point, and ultimately shear failure. This work extends the applicability of time-frequency domains coupled analysis method, and provides practical engineering significance for dynamic deformation and damage identification in complex slopes under coupled seismic-rainfall.