Comparison of Three Commonly Used Equations for Calculating Local Scour Depth around Bridge Pier under Ice Covered Flow Condition

Mohammad Reza Namaee,Jueyi Sui,Yuquan Li,Todd Whitcombe

doi:10.4236/wjet.2018.62b006

Abstract

A precise prediction of maximum scour depth around bridge foundations under ice covered condition is crucial for their safe design because underestimation may result in bridge failure and over-estimation will lead to unnecessary construction costs. Compared to pier scour depth predictions within an open channel, few studies have attempted to predict the extent of pier scour depth under ice-covered condition. The present work examines scour under ice by using a series of clear-water flume experiments employing two adjacent circular bridge piers in a uniform bed were exposed to open channel and both rough and smooth ice covered channels. The measured scour depths were compared to three commonly used bridge scour equations including Gao’s simplified equation, the HEC-18/Jones equation, and the Froehlich Design Equation. The present study has several advantages as it adds to the understanding of the physics of bridge pier scour under ice cover flow condition, it checks the validity and reliability of commonly used bridge pier equations, and it reveals whether they are valid for the case of scour under ice-covered flow conditions. In addition, it explains how accurately an equation developed for scour under open channel flow can predict scour around bridge piers under ice-covered flow condition.

Highlights

IntroductionTo safely design bridges located on waterways under severe flooding conditions, many researchers have developed a number of laboratory-derived equations for predicting bridge pier scour depth [6] [7] [8] [9] [10] [11] [12]
A precise prediction of maximum scour depth around bridge foundations under ice covered condition is crucial for their safe design because underestimation may result in bridge failure and over-estimation will lead to unnecessary construction costs
The present work examines scour under ice by using a series of clear-water flume experiments employing two adjacent circular bridge piers in a uniform bed were exposed to open channel and both rough and smooth ice covered channels

Summary

Introduction

To safely design bridges located on waterways under severe flooding conditions, many researchers have developed a number of laboratory-derived equations for predicting bridge pier scour depth [6] [7] [8] [9] [10] [11] [12] These equations are mostly empirical formulae which are usually based on regressional analysis of laboratory and/or field scour data. The winter season is often overlooked even though most rivers in Canada and northern parts of the United States, Europe, and Asia are annually affected by ice. The relatively smaller number of studies on the scour around bridge pier under ice-covered flow condition is due to the inherent difficulty in collecting field data while ice is present and complications in lab-based measurements as a result of different scales and of temperature effects [13]. Ice cover can lead to issues such as ice jamming, flooding, restricting the generation of hydro-power, blocking river navigation, and affecting the overall ecosystem bal-

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