Experimental study on site and topographic effects on seismic responses in single-sided slopes

Topographic effects can alter seismic ground motion characteristics, resulting in complex seismic responses on slopes, ridges, and other irregular terrains. While the significance of topographic amplification has been observed in historical earthquakes and extensively studied, quantifying and parameterizing the variations in seismic motion caused by these effects remains challenging. This study investigates the seismic responses of single-sided slopes under topographic and site influences using geotechnical centrifuge modeling. Various input motions, including actual earthquake records, were applied to identical slope models with different subsoil thicknesses. The results revealed that topographic amplification at the slope crest was frequency-dependent, contrary to the conventional assumption of uniform topographic amplification factors. Significant resonances were identified at specific frequencies associated with topographic and site features, leading to notable crest amplification. Amplification was further enhanced when the resonant frequencies of topographic and site features converged. Through comprehensive analysis in the time, frequency, and time–frequency domains, we evaluated the resonant frequency bands induced by topographic and site features and their amplifications. Additionally, the study confirmed that the seismic responses of the slope models to actual earthquake motions closely resembled those of sinusoidal waves with similar frequency characteristics, supporting the reliability and field applicability of the findings. These insights improve our understanding of topographic and site effects on seismic ground motion and highlight the need to accurately incorporate these effects into design spectra for regions with complex terrain.