VIRTUAL MASS EFFECT ON SUBMERGED EARTH AND ROCK-FILL SLOPES UNDER VIBRATIONS

Abstract

Normally the hydrodynamic pressure on structures in water are evaluated by applying Nestergaard'a theory or Zanger's theory. These theories consider the stsucturo to be rigid. Same theories are adopted while computing hydrodynacic pressures on earthen and rock fill dams • in case of masonary dams the hydrodynamic. pressure acts on the upstream surface• But the action of water is a little different in case of rock fill dams• 3h• action of water is not only confined to the upstream face but has also access into the pores • The reservoir water in this case is able to communicate .with the water inside the pores• In this thesis virtual masses on sand or gravel slopes representing upstream face of earth dams have been found erperimantally• A comparison Is made with the reoults obtained by applying Zanger's theory treat-ing the dam as an impervious rigid body. The author has also tried to determine the effective unit weight of the fill which should be considered while computing the inertia force. Effect of reservoir water on the damping of the structure is also observed • It is observed that the added mass obtained experimentally is lesser than that obtained by Zanger's theory. The dacping however increaan with increase In the level of reservoir Hater•