Stability evolution and failure mechanism of debris slope under seismic load

• A debris slope model with conical topographic features was developed, revealing the evolution mechanism under seismic loading through shaking table tests and numerical simulations. • Pronounced surficial and elevation amplification effects are exhibited in slope acceleration responses, particularly in the mid-upper convex region, with expansion occurring as amplitude increases. • A four-stage evolution process under seismic loading is revealed through shaking table tests and simulations: localized loose particle sliding, crack formation, crack penetration, and overall instability. This study focuses on typical debris slopes in Qambo City, Tibet. An indoor model with typical debris slope geomorphological features was established. Through shaking table tests and numerical simulations, the dynamic response characteristics and instability evolution mechanisms under seismic load were investigated. The results reveal significant surficial effects and elevation amplification in peak ground acceleration (PGA) and peak ground displacement (PGD) responses, with pronounced acceleration amplification in the convex mid-upper slope regions. The extent of the amplified acceleration zone increases with higher amplitudes of seismic load. Dynamic earth pressure responses indicate that under low-amplitude vibrations, the slope primarily undergoes compaction (positive pressure), exhibiting elastic behavior. In contrast, under high-amplitude vibrations, loosening (negative pressure) dominates, leading to increased internal shear strain, structural stiffness degradation, reduced natural frequency, and accelerated energy accumulation, ultimately triggering instability. When the seismic wave frequency approaches the slope’s natural frequency, resonance effects are induced, forming extensive plastic zones and causing damage to propagate from the mid-slope toward the crest and lateral boundaries. Slope failure primarily originates in the geometrically abrupt mid-upper regions, with slip surfaces typically developing in the convex mid-slope rather than at the toe. The experiments and simulations further demonstrate a four-stage evolution process under seismic loading: particle sliding, crack initiation, crack propagation, and overall instability. This culminates in the formation of a continuous shear slip zone, characterized by a combined tensile-shear failure mode. These findings provide a theoretical basis for understanding landslide development in seismic zones, improving seismic design methodologies, and enhancing disaster resilience for mountainous infrastructure.