Simplified displacement-based methods developed based on sliding blocktheory are widely used in geotechnical engineering practice to predict seismicdisplacements of earth dams and embankments. These methods are typically selectedbecause of the relatively low computational effort that they require, in combinationwith their perceived tendency to provide a reliable index of seismic slopeperformance. In this paper, a previously published database of observed seismicdisplacements for 122 earth dams and embankments was used to evaluate theaccuracy of predicted seismic displacements from six simplified sliding blockmethods. Residual error analysis was performed to compare the model-predictedvalues with those that were observed after seismic shaking. Results show that all ofthe models that were examined have the tendency to underpredict seismicdisplacement, which is of concern as it can lead to unconservative engineeringdesign. This tendency for underprediction cannot be clearly attributed to a singlephenomenon – the authors hypothesize that it may be due to a combination of factorsincluding: the inherent limitations and simplifying assumptions of the underlyingsliding block theories that were used to develop the simplified sliding block models,the inherent inability of sliding block models to capture the earthquake-inducedvolumetric compression that occurs in an embankment during shaking, and/or cyclicstrain softening during earthquake shaking, which can decrease the criticalacceleration during a seismic event.
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