Numerical study on seismic response of a rock slope with discontinuities based on the time-frequency joint analysis method

Abstract

To clarify the seismic response of rock slopes, a time-frequency joint analysis method with the combined use of time, frequency and time-frequency domain analysis is proposed. The dynamic response of a rock slope with discontinuous structural planes was investigated using the finite element method (FEM). A two-dimensional model incorporating finite element meshes with infinite element boundaries for the slope was used in the FEM dynamic analyses. The numerical results show that the elevation, structural plane and direction of wave propagation have an impact on the slope amplification effect. The peak ground acceleration (PGA) under horizontal seismic excitation is approximately 1.2–1.3 times that under vertical seismic excitation. In addition, the first three natural frequencies of the slope can be obtained from the Fourier spectrum and modal analysis. The low-frequency components (<20 Hz) and high-frequency components (>20 Hz) mainly induce the overall and local deformation of the surface slope, respectively. Moreover, the dynamic response of the slope was further investigated by analysing the seismic Hilbert energy. The seismic Hilbert energy in the Hilbert energy spectrum and marginal spectrum is mainly distributed in the low-frequency and high-frequency regions, respectively. The applicability of the Hilbert energy spectrum and marginal spectrum to analyse the dynamic deformation characteristics of the slope is identified. Moreover, the relationship between the local dynamic deformation response of the slope and the occurrence of a landslide was discussed. The dynamic failure mechanism of the slope was clarified according to the frequency-domain and time-frequency domain analysis.