Evaluating Seismic Stability of Embankment Dams - Multiscale Geomechanics: From Soil to Engineering Projects - page 335

years old). Tani [TAN 01] pointed out that the major cause of these failures is the
liquefaction of the foundation or embankment.
The first seismic failure mentioned in the literature is the Manno-Ike Dam in
Japan, occurring one month after the Ansei Nakai earthquake (1854). The failure
was probably caused by the piping. The post-seismic re-assessment concludes that
dams on sandy soil experienced the heaviest damage, suggesting that liquefaction is
their cause.
Among the 1,200 small dams affected by the earthquake in Hyogo-Ken Nanbu
(Kobe M = 7.2) on January 17, 1995, only nine were seriously damaged. On the
island of Awaji, 950 small dams were damaged from among the 24,000, two of
which broke. The failure of the 5.5 m Idenoshiri-Ike embankment, 155 m in length,
occurred 7 s after the beginning of the earthquake when the site acceleration reached
0.45 g, according to Uchida Kazunori et al. [KAZ 01]. Liquefied areas in the
foundation (SPT <5 in Figure 10.2) began at the toes and moved forward and
backward, causing a downstream sliding when they met under the dam axis.
Figure 10.2. Failure of the Idenoshiri-Iki Dam (Japan, 1995)
On the island of Honshu, the majority of damaged dams are between 10 and
25 km away from the fault. Tamostsu Matsui et al. [MAT 01] consider that for an
earthquake within a distance of 5 km, the dominant influence is maximum
acceleration, and thereafter the resonant frequency of the soil governs the behavior.
On the island of Honshu, the 12 m homogeneous Sugatadani-Ike Dam was built with