This study has been conducted to evaluate the effect of mechanical properties of materials of isolation layer to improve the seismic response of gravity dam. To achieve an innovative solution in the present study, a soft layer is assumed to be attached to the upstream face of the dam. This layer which partially absorbs the incident pressure waves from the reservoir is referred to as the isolation layer. Due to the finite thickness and geometry of the concrete dam, the reflected waves from the downstream face of the dam and the dam-layer interface may slightly alter the equivalent value of the wave reflection coefficient at the upstream face of the dam.The Koyna dam is modeled as a case study to indicate the effect of isolation layer on seismic response of gravity dams.

A flexible layer attached to the upstream face of dam and the upper level of foundation under different thickness and height is considered. The response of un-isolated dam is compared with an isolated dam under various condition. Consider to obtained results, it is revealed that the isolation layer can have the reducing effect on responses of dam model because of damping the induced hydrodynamic pressure due to earthquake.