Radar measurement of bridge scour

Scour around bridge piers and abutments has resulted in many structural fai lures over the past decade and considerable research has been carried out t o develop methods which can be used to evaluate the risk of scour affecting the integrity of these major structures. Traditional site investigation me thods based on borehole core and samples of the riverbed sediments are expe nsive and time-consuming and may not always give a complete assessment of t he lithological variation in the riverbed sediments. Geophysical methods ca n be used to determine the riverbed profile beneath the water in a river an d may also be of value for obtaining the previous scour history below the r iverbed level. Trials of ground penetrating radar (GPR) have indicated that this geophysic al method is particularly effective in determining the subbottom geological structure in a shallow freshwater environment, In this presentation the re sults from a number of scour surveys using GPR are presented and discussed. It is concluded that GPR surveys can be effective in determining both the water depth and sub-bottom geological structure near bridge piers and abutm ents provided that the correct instrumentation and operational procedures a re adopted. (C) 1999 Elsevier Science Ltd. All rights reserved.