SYNOPSISThis paper compares two well-established but different methods for frequency-domain analysis of earth dams. The first method is shear beam approach which is an analytical technique for estimating the natural modes and frequencies of vibration of earth dams. The second method is the dynamic finite-element modal analysis approach which is a numerical technique that can predict the actual dynamic response of earth dams. Although both methods attempt to predict the same physical mechanism, they usually yield completely different results. This paper aims at quantifying the "error" from shear-beam analysis, as compared to the more accurate finite-element analysis.

SYNOPSISThis paper is concerned with the future design of new and the assessment of existing earth dams. It aims to understand what the effect of a soft soil foundation for earth dams is. The effects of a compliant foundation are more pronounced under dynamic events such as earthquakes. This study uses dynamic finite element analysis to investigate the dynamic response of earth dams during earthquakes. It is shown that the presence of a soft foundation layer increases the fundamental period of vibration of the dams and depending on the properties of the dam and foundation it may lead to amplification or de-amplification of the seismic accelerations. This is an important observation as design codes (e.g. EC8) need to consider the frequency content of the earthquake and the natural frequencies of the dam structure. Therefore, this study may lead to a better seismic design of earth dams.