Geoscience Reference
In-Depth Information
10.2.5.
Earthquakeperformanceoftailingdams
Nine failures of tailing dams were reported by ICOLD (2001) in
Technical
Bulletin 120
. In 1965, following the La Ligua earthquake (M = 7.1) in Chile, several
tailing dams broke: El Soldado, La Patagua, and El Cobre. The mudslide caused by
the failure of the El Soldado Dam (H = 35 m) caused 200 fatalities. In Peru, the
Shorey Dam failed in 1969 and that of Huachocopolca in 1970. In 1971, three other
failures occurred in Chile: Salamanca and Illapel under a M = 7.1 shake and Cerro
Negro with a M = 7.5 shake. This last fill was broken again in 1985 under a stronger
earthquake of M = 7.7. It is also interesting to note that the Izu-Ohshima earthquake
(M = 7.0) in 1978 broke the first embankment of the Moshikoshi Tailing Dam,
completed in Japan in 1964, during the main shock and the second embankment
during an after-shock.
10.2.6.
Earthquakeperformanceofroadembankmentsandlevees
Tamotsu Matsui
et al.
[MAT 01] have analyzed the factors of harm to wooden
houses and networks during the Kobe Hyogoken-Nambu earthquake. They show
that the seismic intensity was particularly strong in a 6 km strip on either side of the
fault. From statistics on the effects of 75 large earthquakes studied since 1885,
Kazue Wakamatsu [WAK 01] identifies the areas most prone to liquefaction in
geological and geomorphologic terms. She noted that it is mostly Holocene
sediments that were liquefied. Current or recently abandoned river meanders are
most prone to liquefaction. For very large earthquakes, Wakamatsu reported that the
most sensitive areas are the recent floodplain deposits or
natural levees along a
river
, because the water table is higher and the sediments are poorly consolidated,
due to
the former river channels and the sand dunes between lowlands
.
The violent Chi-Chi M = 7.3 earthquake in Taiwan on September 21, 1999
caused 2,400 fatalities, injured over 10,000, damaged over 100,000 houses and led
to more than 2,000 landslides. The lands most prone to liquefaction were polders,
the alluvial deposits of ancient riverbeds and recent deposits along the banks. The
soil in these zones is generally sandy, with a water table between 1 and 3 m deep
and SPT (Standard Penetration Test) number counts less than 10. Settlement and
displacement of many levees within these areas reached 1.5 and 2 m, respectively,
with peak accelerations of up to 0.75 g.
10.2.7.
Earthquakeperformanceofriverhydroelectricembankments
The embankments along the Danube are regularly shaken by earthquakes in the
Vrancea region, for instance with a magnitude of M = 7.2 (1977), M = 6.9 (1986)
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