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the following text, attention will be paid to the conditions of sliding that could cause
collapse and release of water.
A distinction is made between large dams and small dams. If the consequences
of the failure of a large dam are considered catastrophic, those of small dams − even
though not negligible − are often socially acceptable to the extent that it is
appropriate to distinguish them, as is the case in Japan. The only valid distinction
between these two categories of dams is the nature of the consequences of a possible
failure. Without data for assessing the importance of such consequences, the ICOLD
distinction between small and large dams will be adopted: all dams with a height
greater than 15 m are considered large dams.
10.2. Observed seismic performance
The pathology of the seismic behavior of dams is very limited in France. The
strong earthquakes with an MSK intensity greater than VIII hit France at a time
before topics or reports existed. However, the international literature every year
gathers the testimonies of more comprehensive data on the impact of earthquakes.
The ICOLD regularly reports the damage that the strongest earthquakes cause on
large dams [ICO 01]. American publications [SEE 73] and, more recently, Japanese
or Chinese publications contain the post-seismic feedback from major earthquakes
such as San Fernando (USA, 1971), Loma Prieta (USA, 1989), Kobe (Japan, 1995),
Chi-Chi (Taiwan, 1999) and Wenchuan (China, 2008) and detailed observations on
the seismic performance of dams.
10.2.1.
Earthquakeperformanceofgravitydams
On April 18, 1906, the Lower Crystal Springs Dam, a 38.5 m high curved
concrete gravity dam, built of interlocking concrete blocks, withstood the San
Francisco earthquake, M = 8.3 (estimated), without a single crack. The active fault
rupture was located less than 180 m from the dam [ICO 01].
The Koyna Dam [CHO 72], built in 1963, is a 102 m high concrete gravity
buttress dam in Iran. Its section is unusual: the 36 m upper part has a very steep
slope H/V = 0.153, whereas the lower part has a more traditional slope of H/V =
0.72. The dam was calculated to withstand a pseudo-static acceleration of 0.05 g. On
December 11, 1967, the dam was shaken by an earthquake suspected of being
caused by reservoir-triggered seismicity [ICO 01] at a distance of 8−13 km and a
depth of 13 km with a magnitude of M = 6.5. An accelerograph in a gallery on the
right bank recorded the maximum values of the components of acceleration as
0.63 g perpendicular to the valley, 0.49 g in the direction of the valley and 0.34 g
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