Experimental investigation of local scour around circular bridge piers under steady state flow conditions

Local scour around bridge piers is one of the main causes of bridge failures. In this study, scour depths and scour hole geometries around circular bridge piers were investigated under clear water scour conditions for various flow rates. The experiments were carried out in a rectangular flume 80 cm wide, 18.6 m long and 75 cm high by using uniform sediment with a median diameter of 1.63 mm and geometric standard deviation of 1.3. The flow rates and approach flow depths were measured with an electromagnetic flow meter and ultrasonic level sensors, respectively. A new empirical equation for the determination of scour depth is proposed based on the experimental findings of the present study and on experimental data available in the literature. The experimental results were also compared with those calculated using several empirical equations developed by previous studies. The proposed new equation to predict scour depth around a circular bridge pier was evaluated in terms of determination coefficient (R-2) and scatter index (SI). The Fisher (f) test was also applied to test the statistical significance of the proposed equation.