PREDICTION OF LOCAL SCOUR AROUND WIDE BRIDGE PIERS UNDER CLEAR-WATER CONDITIONS

Abstract

Local scour is the removal of sediment from around bridge piers due to flowing of water. A
large amount of local scour is dangerous to the bridge piers and causes the structure tend to collapse and loss
of life without any warning. Many researchers have already investigated the phenomenon of local scour
around bridge piers. The literature search revealed that there is very little information on predictive equations
or data on scour around wide piers. Most of the predictive equations in the literature are intended to apply
equally well to large and small piers. Hence, this leads to a situation in which design is prioritised over
prediction, which thus proves costly and economically inefficient. This study attempted to fill this gap where
new experimental data from a physical model of scouring around a cylindrical and rectangular wide pier
embedded in two types of uniform sediment beds are presented. The effects of sediment sizes and various
pier widths on equilibrium scour depth of wide bridge piers are described. New empirical relation for the
estimation of non-dimensional maximum scour depth for a wide pier were proposed as functions of the
sediment coarseness. The experimental data obtained in this study and data available from the literature are
used to validate the predictions of existing methods and the accuracy of the proposed method. The proposed
method gives reasonable scour depth predictions and was verified with statistical methods where the root
mean square error was reduced from 71% to 26%. The new empirical relation agrees satisfactorily with the
experimental data.