Riprap Sizing for Pile Groups

Abstract

This work presents results on riprap sizing for pile group protection against local scour. Shear failure mechanism is addressed, avoiding edge, bed-form undermining, and winnowing modes. The influences of the flow conditions and the distance between the piles are analyzed. As a result of a laboratory experimental campaign, and within a detailed dimensional analysis framework, the writers propose expressions for riprap block size to resist shear failure. The influence of the distance between the piles on the block size is shown to be small, and the proposed expressions compare well to some of the literature expressions for single piers.