Temporal scouring and backfilling processes around a pile group subject to unsteady hydrographs

Pile groups are important hydraulic structures and scouring around them is not only affected by the flow characteristics but also by the number and arrangement of piles in a group. This research experimentally investigates the temporal scouring around pile groups subjected to single peak hydrographs in clear-water conditions. Results show that the scouring depths around rear piles downstream of the lead could be decreased during the hydrographs by up to 24% of the pile diameter, and that the final scour depth is different from the maximum scour depth. This backfilling process is originated from washing the deposition zones to the downstream piles during the falling limb and affected by the hydrograph unsteadiness properties.