Cumulative damage and stability analysis of bedding rock slope under frequent microseisms

Micro-seism frequently occurs in the Three Gorges Reservoir after impoundment and has a significant impact on slope stability. To investigate the cumulative damage and stability of typical bedding rock slope under frequent microseisms, the shaking table model tests and UDEC discrete element numerical analyses are conducted. The results indicate that: (1) The damping ratio, damage degree and damage rate of slope increase with the increase of seismic duration, while the natural frequency and PGA amplification coefficient decrease. The PGA response of slope shows "elevation effect" and "surface effect". (2) The non-linear cumulative damage model under high and low seismic amplitudes can be represented by exponential and cubic functions respectively, and the evolution curve shows "S" characteristics of slight decline in initial stage, linear increase in intermediate stage and gentle increase in later stage, and "steep" characteristics of rapid rise. (3) The gradual process of cumulative damage and instability is as follows: undulant body climbs, shear and grinds, cracks initiate, propagate and run through, the slope slips wholly along the composite sliding surface, and rock mass accumulates at the slope foot in the form of broken, large and giant blocks. The stability of slope with undulant body is better. (4) The critical times of microseism decrease and the cumulative permanent displacement increases with the increase of seismic amplitude, frequency, slope height and slope angle and the decrease of bedding thickness, and accordingly the stability factor decreases. The slope with outcropped bedding is more prone to fail.