Simplified Methodology for Consideration of Two-Dimensional Dynamic Response of Levees in Liquefaction-Triggering Evaluation

Abstract

Levees are very challenging engineering structures to study, in part because they are not typically well-engineered structures. Unfortunately, there is little to no guidance as to how to evaluate the seismic vulnerability of levees. This study focuses on systematically studying the dynamic response of levees using a wide range of input ground motions and developing a simplified procedure for the liquefaction triggering evaluation of earthen levees, accounting for the dynamic response of the levee. The study was based on three levee sites representative of three select California Central Valley regions; however, because floodplains tend to generally have similar depositional environments, the study can be extended to other regions as long as some of the principal characteristics are still applicable. A wide range of input ground motions was used to capture and assess the variability in response and performance because of multiple possible earthquake scenarios. Two aspects of the dynamic response and performance of earthen levees are presented in more detail: the site and topographic effects on the peak ground acceleration, and the shear stresses and the cyclic stress ratios for a series of profiles throughout the levee sites. A simplified methodology for assessing the factor of safety against triggering of soil liquefaction is developed, and recommendations for applying the methodology are presented and discussed.