A Study on Determination of the Fundamental Period of Earth Dams through Experimental, Empirical, Numerical, and Analytical Methods

Various methodologies for estimating fundamental periods in earth dams have been developed, each striving for supremacy within their domain. Field methods, particularly the Crest-Foundation method (C-F), have emerged as the standard and are acclaimed for discerning the fundamental period of earth dams. This recognition holds true whether calculations are conducted using RFAS or SSR approaches.

This review contributes to improving dam engineering practices and addressing debates on natural period estimation methods by offering a novel and validated approach.

The study conducts a detailed examination of common methodologies for estimating natural periods in earth dams, aiming to enhance their practical applicability. It provides a comprehensive overview, exploring the strengths and limitations of these techniques, and synthesizing relevant studies assessing their effectiveness. It is crucial to note that discrepancies can arise between results from different methodologies, often stemming from various sources such as computational inaccuracies and inherent measurement imprecisions. As such, engaging in a comparative analysis of these methodologies serves not only to refine their calibration but also to propel the advancement of novel techniques, substantiating their validity as promising instruments for conducting dynamic analyses of earth dams.

When comparing results from various other methodologies with the reference method (C-F), subtle discrepancies arise with HVSR analysis based on ambient vibrations, exhibiting a discrepancy of approximately 6%. Additionally, the disparity between fundamental period calculations using the Shear Beam Method (SBM) and the C-F method is around 9%. Empirical formulas, on the other hand, consistently yield results that exceed C-F measurements by approximately 17% on average. Conversely, the gap significantly narrows when comparing outcomes from numerical methodologies, notably the Finite Element Method (FEM), reducing to a mere 1%. FEM, known for its ability to handle complex geometries, is recognized as the more effective tool for capturing structural responses with heightened precision. In this regard, this study introduces a new use of FEM for accurately determining the natural frequencies of earth dams. Through meticulous parameter selection and rigorous validation against empirical data, it presents a refined formula for natural period calculations, especially effective for dams over 50 meters high. Hence, it validates the precision of FEM, offering a reliable alternative for dynamic dam analysis.