Comparative Study of Equations to Predict the Bridge Piers Local Scour with Field and Laboratory Data

In this study, ten formulae were selected for the comparison process using field and laboratory data. First, the effect of the pier shape was studied using laboratory data. The comparative study showed that the Su equation predicts with high precision the scour depth in circular piers, while in rectangular and round piers underestimates it. In case of rectangular piers, the Laursen and Toch and the Ab Ghani and Nalluri equations predict well reasonably the scour. In round piers, the Shen et al. and the Johnson equations provide satisfactory results for scour. It was found that the Hancu equation is not recommended to predict the scour for any cases. Then, using field and laboratory data, for circular piers, it was found that the Hancu and the Melville formulae over-predict greatly the scour depth. The Breusers et al. equation shows great dispersion in the points. This leads to high prediction errors. The Ab Ghani and Nalluri, CSU and the Jain and Fisher formulae predict with high precision the experimental and field scour depths. The Laursen and Toch and the Johnson equations give also good results, but they appeared to over-predict with greater proportion the scour in some flows. For the analyzed field data, the majority of formulae over-predict the scour, while the Shen et al. formula under-predicts it.