Shaking table test on the seismic failure mechanism of a deposit slope with a weak interlayer: Insights from Hilbert-Huang Transform analysis

Earthquakes are critical triggers for slope instability. While extensive research has been conducted on slope failure modes under seismic loading, the identification of sliding surface propagation and coalescence remains insufficiently explored. This study investigates the dynamic response of a deposit slope containing a weak interlayer through large-scale shaking table tests. The propagation process of the sliding surface was identified using the Hilbert-Huang transform and marginal spectrum analysis. Under seismic excitation, sliding occurs along the interface between the overburden and the weak interlayer, leading to sudden landslide events. Differential vibrations at the overburden–weak interlayer–bedrock interfaces are identified as a primary mechanism driving landslide initiation. As input acceleration increases, these interfacial vibration contrasts intensify, and the acceleration amplification effect within the overburden becomes markedly pronounced. Following landslide occurrence, the vibration differences across interfaces decrease sharply. In the time-frequency domain, seismic waves transmitted through the weak interlayer exhibit amplified low-frequency components. Marginal spectrum analysis of seismic energy evolution within the slope reveals that energy attenuation in the 19–22 Hz frequency band correlates with landslide occurrence, while attenuation in the 9–11 Hz band serves as an indicator for sliding surface propagation and coalescence. For seismic design of deposit slopes with weak interlayers, particular attention should be given to the increased seismic inertial forces in the overburden layer and the detrimental effects of low-frequency wave components on sliding surface development.