New Formula for Calculating Local Scour around Bridge Piers

Abstract

Several researchers working on the axes of solid particle transport, river flow, as well as the vulnerability of structures built on rivers have focused their work on the phenomenon of local scour, where many scour formulas have been proposed. Most of these formulas have been developed using laboratory data, estimated from simplified scaled-down models. This led to uncertainties and considerable inaccuracies in the scour estimation, sometimes causing serious consequences for the stability of structures subject to scour. These formulas were rarely tested using field data, where, until recently, there was very little data to validate them. This study aims to propose a new local scour formula using multiple nonlinear regression (MNLR). The data used is in situ data from an extensive database. The new proposed formula includes different parameters of the three fields involved in the triggering and development of the local scour, namely; the bridge, the flow, and the suspended characteristic of the eroded particle. The results obtained in the training phase and the validation show relatively better performances of the new formula compared to the existing empirical formulas.

Analysis of Variables Influencing Scour on Large Sand-Bed Rivers Conducted Using Field Data

“…Based on the PCA results, 5 variables were discarded from further analyses, and all remaining variables can be classified into the following categories: pier geometry (b, l, and bef), hydraulic (y, v, τ, and Fr), compounded hydraulic-sediment variables (vc, Frc, and Frd), sediment properties (d50, τc, and Rep), and channel properties (B and S). Previous studies have concluded that d50 can be eliminated from the development of the scour equation since its range of values is small when compared to the other variables, which consequently leads to biased results [19]. Since only field data are used in this study, d50 is expected to be negligible due to reaching large values of the ratio b/d50 [45,46].…”

“…With the aim of avoiding extrapolation issues, the accuracy of these models should be additionally confirmed with field measurements. Therefore, it is necessary to gain a perspective on scour potential under field conditions [19]. Regardless of the data collection method, most of the scour prediction equations are based on conventional regression methods to provide explicit expressions that are easy-to-use and readily applicable to practice.…”

Analytic network process for local scour formula ranking with parametric sensitivity analysis and soil class clustering

“…Local scour is one of the main events that can threaten the stability of bridges built across rivers. This phenomenon appears as soil erosion on which the bridge piers are supported (Pandey & Md Azamathulla 2021), eventually collapsing the bridge with overall soil erosion (Annad & Lefkir 2022b;Devi & Kumar 2022). Owing to this phenomenon, significant losses in human life, property, and consequently the economy are continuously reported everywhere around the world (Toth & Brandimarte 2011;Bestawy et al 2020).…”

“…Several researchers have proposed various empirical formulas for predicting scour at bridges (Annad & Lefkir 2022b). However, it should be noted that most of the formulas claimed to calculate field scour at the bridge piers were developed using laboratory data, where these formulas have rarely been validated by field measurements.…”

“…As mentioned earlier, it appears to be a fact that many of the empirical formulas do not always provide an efficient assessment of local scour. Moreover, some of these formulas may be suitable for a specific condition but fail in another context (Annad & Lefkir 2022b). This deficiency is probably due to the development conditions of the formulas (i.e., the latter are based on laboratory data that are not able to reproduce a complex field situation) (Vonkeman & Basson 2019).…”