Understanding the destabilization mechanisms in bedrock and overburden layer slopes influenced by both rainfall and seismic activity is of significant engineering importance. A series of large-scale shaking table model tests was conducted to investigate the instability evolution in bedrock and overburden layer slopes after rainfall and seismic events. This study identifies and assesses degradation modes based on spatial deformation characteristics and slope surface displacement patterns. It integrates soil stress-strain behavior

permeability characteristics

seismic stress distribution

and slope deformation characteristics to explore the deformation mechanisms in bedrock and overburden layer slopes after rainfall and seismic events. The results indicate: (1) During rainfall

saturation significantly increases at the slope crest and toe

leading to notable strength degradation without significant overall deformation. However

during seismic activity

the slope crest initially experiences sliding failure

evolving into multi-stage sliding instability. (2) Macroscopic damage occurs suddenly

and the spatial strain distribution within the slope better identifies the evolution of plastic zone expansion

penetration

and instability. (3) The slope’s instability evolution pattern

analyzed by residual displacement ratios

aligns well with the spatial strain evolution within the soil

showing greater sensitivity in identifying the slope’s damage state compared to cumulative displacement. (4) Changes in moisture content affect soil mechanical properties

and post-rainfall infiltration field distribution affects the slope’s overall mechanical behavior and the transmission and spatial distribution of seismic stress. Soil mechanical properties and dynamic stress spatial characteristics determine the slope’s failure modes.