Closure to “An Analysis of Relief Bridge Scour”

Abstract

Based on the proposition that the limit of clear-water scour is a boundary &hear equal to the critical tractive force, a relationship for the scour in a tong contraction as a function of the geometry, the flow, and the sediment has been obtained. Certain assumptions were made to describe the determining ~'factors, but any other methods of evaluating these factors should produce similar relationships. The solution for the long contraction was modified for the abutment and the pier by assuming that the scour holes forming around these .ijbbstructions would1be a multiple of the scour in an imaginary long contraction the width of the scour hole. An approximation of the modified solution for the abutment and an approximate sediment-transport· equation were used to describe the development of the scour hole with time. Comparisons of the relationships obtained by these approximate analyses With measurements from several laboratories indicate that the predictions are reasonably satisfactory and that the method of attack is promising.