RESPONSE OF CONCRETE DAMS ON RIGID AND SOIL FOUNDATIONS UNDER EARTHQUAKE LOADING

Abstract

Dynamic response of dams under earthquake loading depends on their foundation stiffness. Additional hydrodynamic pressures are generated not only by the ground motions but also due to the dynamic response of the dam to the ground motions. The magnitude and distribution of hydrodynamic pressures vary and these effect the deformation of dam which in turn influences the pressure. This paper aims at investigating the effect of dam–foundation interaction on the dynamic response and consequent development of hydrodynamic pressure on dam face using dynamic centrifuge modelling technique. From a series of centrifuge tests it was found that the inclusion of a flexible foundation significantly reduces the dynamic response of the dam. Significant correlation was also observed between the dynamic response of dams and the hydrodynamic pressures developed on their faces. Comparisons with theoretical hydrodynamic pressures show that Westergaard's equation gives a conservative estimation of hydrodynamic pressures during most nonresonant vibrations. Comparison with Chopra's method revealed that it severely underpredicts hydrodynamic pressures for low reservoir depths. However, it yields a reasonably good approximation of the hydrodynamic pressures for higher depth of reservoirs during nonresonant vibration.