Clear‐Water Scour around Bridge Pier Group

TLDR

Recent attempts to reduce scour around solid circular piers have employed riprap, circular collars, rectangular slots, and delta wing‑like fins. The study proposes replacing a solid pier with a group of three smaller piers as a new scour‑reduction device. The authors define a full pier group as extending from foundation to full flow depth, and a partial pier group as extending only partially into the flow depth. The full pier group reduces scour by about 40 %, with a partial group achieving 75 % of that reduction by extending only to half the flow depth; it outperforms a solid cylinder with a full slot of half its diameter and matches a solid cylinder with a collar 3.5 times its diameter, while a collar on a pier group is much more effective than on a solid pier.

Abstract

Recent attempts have been made to reduce scour around solid circular piers. Such attempts use riprap, a circular collar around, a rectangular slot through, and a delta wing‐like fin ahead of piers. Providing another scour reduction device, the present paper replaces the solid pier by a group of three smaller piers. A pier group starting from its foundation and extending fully into the flow depth is termed a "full pier group" and one extending partially into flow depth a "partial pier group." It was observed that the scour reduction due to a full pier group is about 40%, and 75% of this reduction can be realized by a partial pier group extending into half the flow depth only. Also, the full pier group is seen to be more effective than a solid cylinder with a full slot of width equal to half its diameter and as effective as a solid cylinder with a collar 3.5 times its diameter. A collar on a pier group is much more effective than on a solid pier.