Ring columns as pier scour countermeasures

Ring columns placed upstream of a bridge pier to protect it from local scouring are typical scouring countermeasures. A series of experiments are conducted under clear-water steady flow (V/Vc ≤ 1) with uniform sediment. Various parameters, such as ring column diameter, thickness, height, and distances between ring columns and the pier, are considered in the study. Laboratory data are used to assess the influence of each parameter on pier scour depth. Experimental results indicate that pores in ring columns provide space for energy dissipation of the downflow, hence, effectively reduce the flow energy impacting the downstream pier. The friction force of ring columns caused by their geometric shape reduces kinetic energy and pier scour depth. In general, it is found that the best pattern of ring columns reduce pier scour depth by 65%.