Seismic failure mechanism investigation of embankment slope based on the CPO-VMD-HT and marginal spectrum method using shaking table test

Several potential seismic source zones are distributed along the Sichuan–Tibet traffic corridor, but the seismic damage characteristics and dynamic failure mechanisms of the embankment slopes along the Lhasa–Nyingchi Railway, a segment of the corridor, remain unclear. By integrating the Crested Porcupine Optimizer (CPO) and Variational Mode Decomposition-Hilbert Transform (VMD-HT), this paper establishes the CPO-VMD-HT algorithm for seismic signals for the first time and puts forward an identification method for the seismic damage mechanism based on the marginal spectrum. The effectiveness of this method is validated through large-scale shaking table experiments conducted on a typical embankment slope. The results demonstrate that the amplification effect of the embankment slope acceleration is mainly triggered by the mutual superposition of the 0–20 Hz seismic energy and the 45–55 Hz resonant energy. When seismic excitation triggers slope resonance, the acceleration amplification coefficient β at the embankment decreases from 2.16 to 1.26. When the input peak ground acceleration (PGA) is 0.5 g, the second highest value area of seismic energy emerges at the left toe of the embankment, with the peak marginal spectrum amplitude (PMSA) reaching 86.27. The first and second plastic zones gradually coalesce and form a sliding surface, driving the embankment slope into the critical state of instability. Through an analysis of the PMSA, differences in the Hilbert energy distribution within various layers of the embankment slope can be discerned, elucidating the development of shear bands and the dynamic failure mechanisms within the slope. Conducted from an energy propagation perspective, this paper clarifies the acceleration amplification effect and seismic failure mechanisms of embankment slopes. It is thus a crucial reference for the safety risk perception and accurate trend prediction of railway slopes in earthquake-prone areas.