TEMPORAL DEVELOPMENT OF SCOUR AROUND WIDE PIERS

Abstract

Local scour depth around bridge piers is time-dependent. It develops asymptotically towards the equilibrium depth of scour under clear-water scour. Scour is the major cause of bridge pier failure. Many equations are available for predicting temporal and equilibrium scour depth. The present study discusses the phenomenon of temporal scour depth variation at wide bridge piers and deals with the techniques for its estimation. Two types of pier shapes (circular and rectangular) were used to collect the data. The rate of local scour, observed for different pier widths and sediment sizes, was recorded. The data indicates that 50% of the equilibrium scour depth (0.5dse) is achieved at a variety of times, which range from 0.7% to 11%, according to the sediment coarseness values. Similarly, 80% of the equilibrium scour depth develops in a time-varying from 10% to almost 50% of the equilibrium time. The upper limit curve for all the data is also presented.