Study of time-depenbent local scour around bridge piers

Estimation of maximum possible scour depth around bridge piers is an important step in the design of bridge pier foundations. Under known hydrological characteristics such as peak discharge and time-to-peak value of design flood hydrograph, smaller scour depths can be obtained compared to the equilbrium scour depths corresponding to clear water conditions. To examine such a phenomenon, time variation of local scour depths around bridge piers has to be determined. To this end, sets of experiments are performed using single cylindrical and square bridge pier models in the laboratory under clear water conditions with uniform bed materials. Semiempirical time-dependent analysis of local scour depths around bridge piers has been conducted using the sediment continuity equation for the scour hole around bridge piers. For design purposes, nondimensional scour prediction curves were prepared in terms of various sediment and flow properties