Temporal development of scour around wide piers

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 dept. The present study discusses the phenomenon of temporal scour dept variation at wide bridge pier and deals with the techniques for its estimation. Two type of pier shape (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 dept (0.5dse) is achieved in a variety of times which range from 0.7% to 11% of te, according to the sediment coarseness values. Similarly, 80% of the equilibrium scour dept develops in a time varying from 10% to almost 50% of the equilibrium time. The upper limit curve for all the data also presented.