A Critical Analysis of Jet-Induced Scour Formulas

Many studies investigate erosive processes occurring in non-cohesive granular materials downstream of grade-control structures, dam spillways, headcuts, and other hydraulic structures. Because of the complexity of the scour mechanism, the analysis of the scour phenomenon caused by plunging jets is generally conducted by using physical models and particularly for specific structure geometries. In this regard, many researchers proposed empirical approaches to estimate the main scour lengths, but their contributions are limited to tested conditions and cannot be generalized. This lack of generality has been (partially) overcome by other, more recent, approaches, that are either semitheoretical or fully theoretical. Previous works assessed the predictive capability of the most well-known empirical relationships but did not present a comparative analysis between empirical and (semi-)theoretical relationships. The aim of this paper is to contribute to fill this gap of knowledge. Namely, we present an experimental validation of the most popular relationships using a large database. In addition, we compare the predictive capability of some (semi-)theoretical relationships with that of the best known empirical formulas. In doing so, we provide interesting insights into the different approaches, highlighting their limits in assessing the main scour features. Overall, this paper provides a critical and updated analysis of different approaches for scour problems caused by plunging jets.