Abstract
Although vertical oscillations may have a profound effect on the seismic stability and deformability of embankment dams, they have received so far little, if any, attention. Filling this gap, the paper develops a simple but realistic two-dimensional method for evaluating the dynamic characteristics and analyzing the seismic behaviour of earth and rockfill dams oscillating in the vertical direction. Shear and dilatational deformations are considered, the dependence of soil stiffness on confining pressure is rationally modeled and the effect of canyon geometry is approximately treated. Numerical results are portrayed in the form of dimensionless graphs of natural frequencies, modal displacement shapes and modal participation factors as functions of characteristic geometric and material parameters. To demonstrate the capability of the developed model to successfully predict the field performance of actual dams, three case studies are presented involving two earth and one rockfill dam from three seismically active countries. Reasonably good agreement is obtained between computed and observed (during earthquake shaking) natural frequencies and vertical crest accelerations.
