Response and modeling of cantilever retaining walls subjected to seismic motions

A series of nonlinear, explicit finite difference analyses were performed to determine the dynamic response of a cantilever retaining wall subjected to earthquake motions. This article outlines the calibration and validation of the numerical model used in the analyses and comparisons are presented between the results from the finite difference analyses and results from simplified techniques for computing dynamic earth pressures and permanent wall displacement (i.e., Mononobe-Okabe and Newmark sliding block methods). It was found that at very low levels of acceleration, the induced pressures were in general agreement with those predicted by the Mononobe-Okabe method. However, as the accelerations increased to those expected in regions of moderate seismicity, the induced pressures are larger than those predicted by the Mononobe-Okabe method. This deviation is attributed to the flexibility of the retaining wall system and to the observation that the driving soil wedge does not respond monolithically, but rather responds as several wedges. Additionally, it was found that the critical load case for the structural design of the wall differed from that for the global stability of the wall, contrary to the common assumption made in practice that the two load cases are the same.