Evaluating Seismic Stability of Embankment Dams - Multiscale Geomechanics: From Soil to Engineering Projects - page 340

features. Few dams were shaken by the maximum design earthquake (MDE), but
some others were shaken by earthquakes larger than the MDE. This observation
shows that there is less than one casualty for nearly one million dam-years and
highlights the real resistance of these engineering works to seismic hazard, as long
as the design respects the post-1959 state-of-the-art rules.
10.2.14. Majorseismicdamageoflargeconcretedams
Concrete dams performed very well under earthquakes. The performance of
gravity dams and buttress dams is similar, as shown by the similarity in performance
of the Koyna and the Sefirud dams: cracks are concentrated near the crest on the
downstream face and around geometric changes in inertia. Apart from this cracking,
their performance remained correct.
The most vulnerable areas are the locations where inertia changed at the crest
and the interface with the foundation. The suspected common failure modes in
gravity dams should be tilting after uplift in an open upstream crack and sliding
along an open joint (see Figure 10.4), tilting along a joint, crushing of the
downstream toe and downward tilting of the foot with crushing. These failure modes
were identified on physical models.
Figure 10.4. Cracking in the Konya Dam (left) and Sefi Rud Dam (right)
More generally, the main mode of rupture of concrete dams subjected to strong
earthquakes is the formation of cracks in areas where the stresses are concentrated,
such as the central part of the crest, and along planes of weaknesses: horizontal
construction joint or vertical expansion joint. It is worth noting that leakages through