Seismic response of embankment dams under near-fault and far-field ground motion excitation

Abstract

The characteristics of near-fault and far-field earthquakes differ. Records suggest that a near-fault ground motion is characterized by a large high-energy pulse and a distinctive pulse shape for the velocity time history. The present study compared near-fault and far-field ground motion effects and investigates the consequence of well-known characteristics of near-fault ground motion on the nonlinear dynamic response of an embankment dam. It was shown that median maximum demands, such as crest settlement and critical slip surface displacement of the embankment dam, were higher for near-fault ground motion than far-field motion. For pulse-type near-fault input, the maximum demand was a function of spectral shape and the ratio of the pulse period to the fundamental period of the embankment dam. Near-fault ground motion with a period pulse 1.5 to 4 times greater than the natural period of the dam created a larger seismic demand than when the pulse period was equal to or smaller than the natural period of dam. This difference increased up to 1.85 times as the ground motion intensity increased. Velocity-related ground motion intensity indices, such as peak ground velocity, were much more effective than peak ground acceleration to correlate with seismic demand. This was because shear stress level has a direct relation with the velocity time history of ground motion.