Analysis of infinite reservoir subjected to earthquake excitation

Abstract

Dam hold huge amount of water. Retained water is used for flood controlling, irrigation and hydroelectricity generation. Accurate estimation of hydrodynamic pressure on Dam is major issue in design of dam. Conventional approach becomes very complex in case of analysis structure having irregular geometry such as Dam. Finite element analysis is the best solution for this issue. Displacement-based approach for modeling of fluid medium may create some spurious mode which has no practical meaning. To overcome this problem Eulerian approach is used for determination of hydrodynamic pressure. In this pressure based approach number of nodal unknown parameter is reduced. Determination of hydrodynamic pressure on concrete gravity dam becomes very difficult due to infinitely extended length of reservoir. To remove this difficulty, the reservoir is truncated at a finite distance from face of dam. Truncation of reservoir also reduces the computational time. For simplification of analytical procedure, the reservoir bottom is assumed as rigid which does not represent actual behavior of the system. Such assumption overestimates the value of hydrodynamic pressure because a part of energy of hydrodynamic waves gets absorbed in sediment deposited at bottom of reservoir. Most of the analysis has been done considering vertical dam reservoir interface. The dam reservoir interface may be inclined in practical scenario. Inclination of dam reservoir interface largely affects the value of hydrodynamic pressure. In present analysis, fluid is considered as non-viscous and linearly compressible. Bottom absorption effect is taken into consideration. Reservoir is truncated at certain distance away from structure to reduce the computational time. Eulerian approach is used to determine the hydrodynamic pressure at face of dam. Finite element method is employed to discretize the reservoir medium. Surface wave is neglected. Dam reservoir interface is considered as inclined to get accurate value hydrodynamic pressure. The analysis is restricted to two dimensional. A MATLAB code is developed for analysis purpose. Hydrodynamic pressure distribution and time history analysis is obtained for harmonic excitation. Again time history plot also obtained for earthquake excitation.