Environmental Engineering Reference
In-Depth Information
FIGURE 11.37
The Lower San Fernando Dam after the San Fernando earthquake of February 9, 1971. A major slide occurred
along the upstream side by liquefaction of hydraulic fill in the dam body. (Photograph courtesy of the U.S.
Geological Survey.)
after the earthquake had continued for some time, when ground motions had
almost ceased following the period of strong ground shaking. The investigators
concluded that since the slide did not occur when the induced stresses were high,
but rather under essentially static load conditions, there was a major loss of
strength of some of the soil in the embankment during ground shaking.
Upper dam : Dynamic analysis indicated that the dam would not undergo com-
plete failure, but that the development of large shear strains would lead to sub-
stantial deformations in the embankment.
Analytical Methods
Dynamic Analysis
The procedure is essentially similar to that performed for structures as described in
Section 11.4. Characteristics of the motion developed in the rock underlying the embank-
ment and its soil foundation during the earthquake are estimated, the response of the
foundation to the base rock excitation is evaluated, and the dynamic stresses induced in
representative elements of the embankment are computed.
 
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