The ability to establish foundation elevations for intermediate bridge piers that will provide a reasonable degree of assurance that the pier will not be undermined by the flowing stream and to rate existing intermediate bridge pier foundations relative to their risk of being undermined has become a matter of national concern. This paper will document the results of a study that presents and recommends formulae that can be used to predict the anticipated depth of local scour in both uniform-particle, cohesion less streambeds, and graded, armoured streambeds. The study incorporated both a literature search and a field verification of the results of the literature search.The Laursen and Toch formula will be recommended to predict anticipated local scour depths at intermediate bridge piers in uniform-particle, cohesion less streambeds, and the university of Aukland formula will be recommended for consideration for graded, armoured streambeds. This document will show that these scour prediction formulae, in conjunction with other engineering data, can be a valuable tool to aid the engineer in economically and safely establishing an intermediate bridge pier foundation elevation, or rating the safety of an existing foundation.
Abstract