Longitudinal Seismic Behavior of Earth Dams

Earthquake-induced vibration in earth darns in a direction parallel to the darn axis is studied using analytical elastic models. The non-homogeneity of the darn materials is taken into account by assuming specific variations of the elastic moduli along the depth due to the confining pressure. Based on the models, a rational procedure is developed to estimate dynamic stresses and strains (both shear and normal) and corresponding elastic moduli and damping factors for earth darns from their hysteretic responses to real earthquakes, utilizing the hysteresis loops from the crest and base records. This leads to a study of the variation of stiffness and damping properties with the strain levels of different loops. Finally, an analysis of real earthquake performance of an earth dam, in the longitudinal direction, yields data on the shear moduli, damping factors, and nonlinear constitutive relations for the dam materials; the Ramberg-Osgood nonlinear stress-strain curves are then fitted to these data