Numerical investigation on seismic dynamic response characteristics of high-steep layered granite slopes via time-frequency analysis

Abstract

The occurrence of geological structure and stratum lithology plays important roles in the seismic stability of complex slopes, which is also the difficult points of engineering construction. Four three-dimensional layered granite slope models with infinite boundary were modeling via finite element method (FEM). Seismic response and deformation characteristics of slopes are systematically studied through time-frequency domain. A frequency-domain analysis method of complex slopes is proposed including modal and spectrum conjoint analysis. Modal analysis can directly display the main vibration modes of slopes. The combination of modal and spectral analysis can clarify the inherent characteristics of slopes, and reveal the interaction mechanism between inherent frequency and dynamic characteristics of slopes. The results illustrate that structural faces have significant effects on the propagation characteristics of wave within rock mass, and complex refraction/reflection phenomena occur near these discontinuities, thus to different dynamic response characteristics in the slope. Layered slopes have apparent magnification effect of slope surface and altitude. Directions of seismic excitation and structural plane types affect the dynamic response of slopes. Horizontal wave mainly affects the middle and upper part of high-steep slope, while vertical wave has obvious influence on the slope crest. Additionally, Fourier spectral analysis shows that structural planes have filtering effects on the high-frequency waves. Combined with modal analysis, it further explains that high-frequency section of waves mainly triggers local deformation of slopes, while low-frequency component controls their overall deformation. Finally, instability regions and evolution process of different layered slopes were predicted based on time-frequency conjoint analysis.