Effects of blockage and relative coarseness on clear water bridge pier scour

Clear water pier scour experiments were conducted in the laboratory to analyze the effects that blockage ratio and relative coarseness have on bridge pier scour depth. For these tests, the blockage ratio and relative coarseness were kept constant for each of the four different sand bed materials and a constant water depth was maintained for all experiments. The flow shallowness varies from values in the narrow pier range for the two coarser sediments to values of very narrow piers for the two finer sediments.;The blockage ratio and relative coarseness were each increased four times, and kept in a range such that it did not make them the controlling factor for the scouring, but still a contributing factor.;The parameters effecting scour were evaluated and compared with the equilibrium bridge pier scour depth. A relationship involving relative coarseness with flow shallowness and equilibrium scour hole depth was found.