CENTRIFUGE STUDY ON VOLUME CHANGES AND DYNAMIC STABILITY OF EARTH DAMS

A simplified method of analysis for determining the permanent displace ment 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 s ubjected to earthquakes large enough to produce flow slides. These stu dies suggest that the failure mode is considerably influenced by the r eduction in shear strength caused by the void-ratio increase and the s ubsequent decrease in effective stress at the sand-clay interface. Con ventional 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 stren gth and the redistributed void-ratio at the interface. Values predicte d using this method were found to agree well with those observed in th e centrifuge experiments. By integrating these quantities into Newmark 's sliding block analysis, a better estimate of the permanent displace ment of an earth dam may be obtained.