Study of Height Effect on Earthquake Modal Response in Embankment Dams

Knowledge of the earthquake behavior of embankment dams comes from four sources: observations made from the dam response during earthquakes, experiments conducted on prototype dams for determination of their dynamic properties, experiments conducted on reduced scale models of dams including shaking table and centrifuge testing and finally analytical studies. From numerical analysis point of view, two dimensional seismic response analyses is usually applied to seismic design of embankment dams. Evaluation of seismic behavior for different height of dam is important. Many embankment dams have been made in different height in the world that we have not general point of view about seismic behavior of them. To achieve this goal, Masjed Soleyman dam for a case study has been selected. Masjed Soleyman zoned rock fill dam with ۱۷۷ m height was constructed and impounded in South-West of Iran in ۲۰۰۱. Finite Element model of Masjed Soleyman dam has been constructed and the Mohr-coulomb elastic-perfectly plastic constitutive model is taken into account to reflect the soil stress-strain relation. First, layer analyses have been carried out considering ۱۲ layers in end of construction stage. Then, this analysis has been continued considering water table and weight of dam reservoir. ۲ earthquake records have been applied horizontally to the bedrock for dynamic analysis. For study of mode of vibration and distribution of acceleration, ۱۰ models have been used with different height. Then seismic response of earth dam due to some known earthquake has been investigated. These data were used to identify the modes of vibration of the dam. Result shows that First and second mode of vibration in Masjed Soleyman dam case to peak horizontal displacement and acceleration decreased in height of dam. Also changing of peak horizontal acceleration and peak horizontal displacement in height of dam depends on dominant mode of vibration, height of dam, properties of materials and frequency specification.

Keywords:

Embankment Dams , Masjed Soleyman Dam , dynamic analyses , Different Height , seismic response