Scour Depth at Bridges: Method Including Soil Properties. I: Maximum Scour Depth Prediction

Abstract

Scour of the soil by flowing water around bridge supports is the number one reason for bridge collapse. Predicting the depth of the scour hole is an integral part of the bridge foundation design, as it impacts the depth of the piles. Indeed, the scour depth must be ignored in the vertical and horizontal resistance of the piles. This paper presents a method to calculate the maximum depth of the scour hole around bridge supports when subjected to a constant water velocity. Most existing methods take into account the water velocity and the geometry of the obstacle but not the soil type. The method presented in this paper keeps those important variables and adds the paramount influence of the soil erosion characteristics. It is developed on the basis of 94 flume tests, some of them very large laboratory-scale tests, as well as dimensional analysis and experience. It applies to pier scour, contraction scour, and abutment scour. The method is evaluated by comparing the maximum scour depth predictions against measured data from 10 databases of pier, contraction, and abutment scour depths.