vulnerable dams, or for purposes of preliminary analysis. For high dams,
or dams in situations where seismicity is considered critical, more
sophisticated procedures are necessary. In such circumstances seismologi-
cal appraisal of the dam site should be followed by a comprehensive evalu-
ation on the basis of dynamic response analysis. Pseudostatic and dynamic
analyses are briefly introduced below.
Kaptan (1999) presents a review of the approach to determining
seismic design criteria for dams in Turkey, a region noted for its high level
of seismic activity. Fundamental criteria for dynamic analysis of embank-
ments and of concrete dams are discussed. They are placed in perspective
by notes on the evaluation of seismic criteria appropriate to the 184 m high
Ataturk earthfill–rockfill embankment and on dynamic response analysis
for the Sürgü rockfill dam of 66 m height.
PSEUDOSTATIC ANALYSIS
The intensity of a shock is expressed by acceleration coefficients h(hori-
zontal) and v(vertical), each representing the ratio of PGA to gravita-
tional acceleration, g. It is frequently assumed that h(1.5–2.0)vfor the
purposes of initial analysis. Representative seismic coefficients, h, as
applied in design are listed in Table 2.8. Corresponding earthquake inten-
sities on the modified Mercalli scale and a qualitative scale of damage are
also shown, together with the equivalent US seismic zone designations.
Values of seismic coefficient greater than those tabulated are appro-
priate to more extreme circumstances, e.g. h0.4 has been employed for
dams on high-risk sites in Japan. (Ground accelerations equivalent to
h0.5 severely damaged the Koyna gravity dam, India, in 1967. Pacoima
arch dam in the USA was similarly severely damaged in 1971 by an event
estimated as equating to a base level horizontal seismic coefficient of
h0.6–0.8.)
94 EMBANKMENT DAM ENGINEERING
Table 2.8 Seismic acceleration coefficients, h, and earthquake intensity
levels
Coefficient Modified General damage US seismic zone
h Mercalli scale level
0.0 – Nil 0 (Note: there is
0.05 VI Minor 1 no direct
0.10 VII Moderate 2 equivalence
0.15 c.VIII–IX Major 3 with UK zones
0.20 Great 4
A, B, C)
0.30 IX Widespread – –
0.40 IX destruction – –
