CENTRIFUGE STUDY ON VOLUME CHANGES AND DYNAMIC STABILITY OF EARTH DAMS

A simplified method of analysis for determining the permanent displacement of a clay core in a heterogeneous earth dam subjected to dynamic excitation is dissussed. Centrifuge studies on three identical models were used to determine the deformation characteristics of earth dams subjected to earthquakes large enough to produce flow slides. These studies suggest that the failure mode is considerably influenced by the reduction in shear strength caused by the void-ratio increase and the subsequent decrease in effective stress at the sand-clay interface. Conventional sliding block analysis does not consider this phenomenon. A simplified method using the concepts of critical-state soil mechanics is presented that may be used to estimate both the reduced shear strength and the redistributed void-ratio at the interface. Values predicted using this method were found to agree well with those observed in the centrifuge experiments. By integrating these quantities into Newmark's sliding block analysis, a better estimate of the permanent displacement of an earth dam may be obtained.