Estimating Deformation of Embankment Dams Caused by Earthquakes

Abstract Only - Previous studies by the author have shown that the amount of deformation that an embankment dam undergoes during earthquake is directly related to the seismic energy produced at the site, as measured in terms of earthquake magnitude and peak ground acceleration. This relationship was developed during an evaluation of written records and a statistical analysis of 42 case histories; the results of these efforts were presented during the Association of State Dam Safety Officials 1993 Annual Conference.

During the past two years, and additional 10 case histories have been added to the database, including six case recorded during the 1994 Northridge, California earthquake. These new cases confirm the previously established relationships. The entire catalog has been subjected to additional analyses to determine in any other factors besides the earthquake magnitude and peak ground acceleration consistently play a role in the relative among of deformation that dams experience during earthquake and can be used to predict related damage levels. The results of these latest studies show that five other factors appear to influence the amount of deformation that can be expected; these include:
1. The distance between the dam and the nearest fault ground rupture,
2. The height of the dam,
3. The depth of alluvium below the dam,
4. The height:crest length ration of the structure, and
5. The type of dam, e.g., rockfill, zoned earthfill, homogeneous, hydraulic fill, etc.

Graphs depicting these relationships are presented and specific case histories that illustrate pertinent points are discussed. Results of previous statistical studies by Japanese authors are compared to the current findings. In addition, the empirical relationships developed in this current study are discussed and compared to some of the more theoretical methods used to calculate amounts of seismic deformation of embankment dams.