Experimental investigation of clear-water local scour at pile groups

Experiments of local scour around pile groups are carried out under steady clear-water scour conditions. A variety of conditions including different pile group arrangements, spacing, flow rates, and sediment grain sizes are considered. In total, 112 experiments are carried out. It is observed that the scour-hole depth for some cases of pile groups increases as much as two times more than its magnitude for the case of single piles. The data from this study and some laboratory experiment data from previous works are used to derive a correction factor to predict the maximum local scour depth for the pile groups. Two well-known equations, i.e., Federal Highway Administration, Hydraulic Engineering Circular No. 18, HEC-18 (reported by Richardson and Davis in 2001) and the New Zealand pier scour equation (reported by Melville and Coleman in 2000) are considered. The prediction of scour hole based on the present correction agrees well with the observations.