Scour Protection at Bridge Piers

TLDR

Pier scour is typically mitigated by coarse riprap and an inverted filter layer, but installing the filter in deep water is difficult, often leading to riprap failure. The study aims to review current scour‑protection methods and propose alternative or additional devices for bridge piers. It evaluates the use of a slot in the pier or a collar around it to control scour depth. Experiments in clear water show that a slot equal to one‑quarter of the pier diameter can reduce equilibrium scour depth by up to 20 %, and adding a collar further decreases scour, indicating these devices can serve as effective scour‑protection options.

Abstract

The objective of this study is to review existing methods and propose alternative or additional devices for scour protection around bridge piers. Engineering methods used in dealing with pier‐scour problems include placing coarse riprap around the foundations. An inverted filter layer is normally placed beneath the riprap to overcome leaching problems. Practical difficulties in laying the filter according to specifications, especially in deep water, often cause failure of the riprap layer. The study examines the effect of using a slot in the pier, or a collar around it, as devices for controlling the depth of scour. Experiments conducted in clear‐water conditions show that the use of a slot alone (with a width equal to one‐fourth of the pier diameter) can reduce equilibrium scour depth by as much as 20%. A combination of slot and collar can further reduce the scour depth. These devices may be useful as additional or alternative devices for scour protection.