The Local Scour Impact Around a Cylindrical Bridge Pier for Two Different Abutment Models

Local scour, the erosion of sediment around hydraulic structures caused by flowing water, is a major factor contributing to bridge failure, particularly near piers and abutments. While scour mechanisms around individual structural components have been widely studied, limited attention has been given to the interactive effects of abutment geometry and spacing relative to piers. This study investigates the influence of two abutment shapes (wing-wall and trapezoidal) on the size and formation of scour holes around a cylindrical pier. Fifty laboratory experiments were conducted in a flume under clear-water conditions, testing two pier–abutment distances (22.5 cm and 17.5 cm) across varying hydraulic parameters. Results indicate that, at a fixed spacing, scour depth around the pier decreases with increased flow depth but increases with higher Froude numbers and flow intensity. When the abutment is positioned closer to the pier, flow convergence intensifies, causing individual scour holes to merge and form a larger scour hole. The presence of abutments increased the scour depth by up to 41.56% for the wing-wall and 52.04% for the trapezoidal model at a 22.5 cm spacing, with a further increase observed at 17.5 cm spacing. Empirical scour prediction models developed using IBM SPSS 30 demonstrated high accuracy, yielding coefficients of determination (R²) of 93.6% and 91.6% for the wing-wall and trapezoidal configurations, respectively.