Catastrophic processes in bedding rock slopes under multiphase seismic actions: Insights from shaking table tests and optical fiber sensing

In seismically active regions, landslides often result from the cumulative damage caused by multiple seismic events. In this study, shaking table tests and optical fiber sensing technologies, including optical frequency domain reflectometry (OFDR) and distributed acoustic sensing (DAS), are employed to investigate the dynamic response and evolution of bedding rock slopes under multiphase seismic activity. This study reveals progressive damage from the interior to the exterior and from local to global scales. The results demonstrate that as the loading phase progresses and slope damage increases, the dynamic response of the slope becomes increasingly nonlinear. The accumulation of residual earth pressure intensifies earth pressure responses in subsequent seismic events. The slope shoulder and toe are identified as preferential zones for dynamic damage development. The variations in peak microstrain as measured by OFDR reflect the spatiotemporal evolution of internal slope damage under complex seismic excitation. Moreover, the time-frequency spectrum characteristics derived from the acoustic sensing signals reveal the overall seismic cracking conditions of the slope. A sudden change in earth pressure or microstrain at the slope shoulder, an increased occurrence of low-frequency high-energy signals in the acoustic sensing time-frequency spectrum, and diffuse distribution of high-frequency components all indicate imminent slope failure. The failure process of the slope under complex seismic action exhibits stage-specific characteristics, each identifiable through typical indicators.