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these cracks lead to important uplift in these joints. Failure would be possible if, on
the one hand, part of the crest or a block was initially isolated from the dam body by
these discontinuities and, on the other hand, pushed to slide or tilt under the inertial
and hydrodynamic forces. To our knowledge, this has not yet happened.
This reassuring feedback has to be taken with caution. The only failure, which
occurred during the Chi-Chi earthquake (1999), concerns a failure mode not
considered by physical models: the Shih Kang Dam moved on an active fault. This
shows that previous or other failure modes are possible because the poorly designed
structures have not been strongly shaken. Although the construction of a dam on an
active fault is not acceptable to the majority of the scientific community, this failure
nevertheless shows the difficulty of investigating and locating active faults.
10.2.15. Seismicdamageoflargeembankmentdams
Embankment dams are more vulnerable to earthquakes than concrete dams. This
vulnerability varies greatly, however, with the type of design. It is important to
remember that no major embankment dam anywhere in the world that has been
constructed in accordance with modern practice or after 1960 has been destroyed by
an earthquake. The only two large dams (H> 15m) that failed were the Chang Dam,
built in 1959 in India, and the Fujinuma Dam, built in 1949 in Japan. Not only did
they not comply with modern rules, but they suffered liquefaction due to a lack of
compaction of their materials or foundations. This lack of compaction means that
the tailing dams are by far the most likely to experience failure.
In conclusion, it is important to remember that liquefaction is the only cause of
failure cited by the previous references. It is the main danger that requires a detailed
investigation to be made on all existing dams. The evaluation of its effects on any
embankment requires either a simplified risk analysis or a simplified coupled
analysis developed later, depending on the issues involved.
10.2.16. Delayedorindirectconsequencesofanearthquake
Feedback shows that delayed or indirect effects can induce failure landslides in
reservoirs, the development of internal erosion through cracks, loss of access by
falling blocks, loss of control by destruction of technical control center and
switching power poles. These are all very serious dangers that must be addressed in
the analysis.
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