Probabilistic assessment of permanent displacement of soil slopes: how many ground motions are needed?

Abstract

As the occurrence of earthquakes is highly uncertain, the permanent displacement of a slope during a given exposure time is also uncertain. Probabilistic analysis can be used to assess the effect of uncertainty in the ground motions on the permanent displacement. However, the number of ground motions to be considered in a probabilistic assessment of permanent displacement of a slope is still not clearly defined. In this paper, a numerical study is conducted to investigate the effect of number of ground motions on the variability of fragility curves and the hazard curve of the permanent displacement. It is found that for the slope study in this paper, the median fragility curve and hazard curve are not sensitive to the number of ground motions. The width of the confidence interval of the fragility curve can be reduced by half when the number of ground motions is increased by four times. It can be learned from the COV of the hazard curve of permanent displacement that the determination of the number of ground motion records should be based on a concerned critical permanent displacement.