Algorithm for Time Domain Reflectometry Bridge Scour Measurement System

Scour contributes to most failures of highway bridges constructed over waterways in the United States. Sediments are washed away by floods and bridge piers are left inadequately supported. Field monitoring of bridge sour process is necessary to study the scour mechanism, to improve the bridge piers and abutments design, to plan an effective remediation measure, and to develop emergency warning systems. The current tools for bridge scour monitoring are generally not satisfactory for these purposes. This study introduces the development of an automatic scour monitoring system using Time Domain Reflectometry (TDR). After briefly present the theoretical bases of TDR for scour detection, a framework for TDR information analyses is developed. Simulated scour and sediment tests were performed with TDR instrument deployed to acquire signals. The acquired data were analyzed using the developed theory. It was found that TDR signal changes have strong correlation with sediment layer thickness changes, as predicted by the theory. From TDR measured apparent dielectric constant and electrical conductivity, the depth of scour were accurately determined.