Effect of excitation frequency and joint density on the dynamic amplification effect of slope surface on jointed rock slopes

This paper presents the slope dynamic response of jointed rock slopes containing three groups of typical joints and analyzes the effect of input harmonic frequency and joint density on the peak horizontal acceleration (PGA) of the slope surface under vertically impinging SV wave (shear vertical wave) excitation. First, the dynamic response of the slope surface of the bedding slope was investigated with a large-scale shaking table test, and the reliability of the numerical model was verified by the physical modeling. Then, a series of jointed rock slope models with different joint densities were established based on the three-dimensional discrete element software 3DEC. It is found that the natural frequency f(n) of the jointed slope decreases with the increase of joint density. The effect of excitation frequency f on the slope surface dynamic response of the jointed slope is stronger than that of joint density. The closer the f is to the f(n), the stronger the slope surface and slope crest dynamic response is. Notably, taking f(n) as the critical value of f, the slope surface dynamic amplification mode of jointed slope can be divided into two types: when f <= f(n), the acceleration amplification factor of X-direction (AAF-X) of the slope surface amplifies monotonically with increasing elevation; when f > f(n), the AAF-X of the slope surface shows a fluctuated amplification pattern with the increase of elevation. The results of this paper show that in the seismic design of slope engineering, the influence of site conditions on the frequency spectrum characteristics of ground motion should be considered, and then the optimal design should be carried out.