Seismic Improvement of Gravity Dams Using Isolation Layer in Contact Area of Dam-Reservoir in Smeared Crack Approach

摘要

This study has been conducted to evaluate the effect of the isolation layer on the seismic improvement of concrete gravity dams considering dam-reservoir interaction. Koyna dam in India, due to both horizontal and vertical components of Koyna earthquake, is modeled as a case study to show the effect of the upstream isolation layer on the seismic response of concrete gravity dams, and also the interaction effect is considered in models. The water is taken as a compressible, inviscid fluid and the foundation as rigid. Gravity dams are considered as 2D structures due to long dimension in cross-stream direction and plane strain assumptions. ANSYS software was used for analysis so that the fixed smeared crack model is used to consider the nonlinear behavior of mass concrete. A flexible layer which is attached to the upstream face of the dam under different thickness and material properties is considered. The response of unisolated and isolated dams is compared under various conditions. Finally, the effect of unisolated and isolated layers in the reduction of the seismic response of the concrete is evaluated under various thicknesses comparatively. Considering obtained results revealed that the layer can have the reducing effect on responses and crack propagation process of dam model because of damping the induced hydrodynamic pressure due to the earthquake.