2017 – Seismic Performance of Existing and New Embankment Dams: The Myth of the Reliability of Simplified Newmark-type Methods

Mojtaba E. Kan, Hossein A. Taiebat and Mahdi Taiebat

In design of new embankment dams or evaluation of the performance of existing earthfill and rockfill dams, the Newmark-type Simplified Methods are widely used to estimate the earthquake-induced displacements. These methods are simple, inexpensive, and substantially less time consuming as compared to the complicated stress–deformation approaches. They are especially recommended by technical guidelines to be used as a screening tool, to identify embankments with marginal factor of safety. The methods would serve as a reliable screening tool had they always resulted in conservative estimates of settlements. However, a number of studies in the last 15 years show the contrary. This paper provides a critical review of the fundamental theory behind the simplified Newmark-type methods. Cases in which the results of the simplified methods are reportedly non conservative are further investigated and possible reasons are discussed, that may be taken into account in future design and investigations of Australian dams. The reliability of the simplified methods is examined based on the existing thresholds proposed in the literature and accounting for the embankment geometry and type, and for the seismic activity characterization. A recently proposed practical framework is further elaborated to demonstrate its effectiveness in the study of seismic behaviour of embankment dams. In particular, the case study of Zipingpu concrete faced rockfill dam in China is discussed where all widely used simplified procedures failed to predict the order of deformations experienced by the Dam under a recent strong earthquake event.

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