Time Domain Reflectometry Automatic Bridge Scour Measurement System: Principles and Potentials

Bridge scour is a major factor contributing to the failures of highway bridges constructed over waterways. During flood events, sediments can be washed away and bridge substructures (piers and abutments) are left inadequately supported. Field monitoring of bridge sour process is necessary to study the scour mechanism, to develop scour-resistant design of bridge piers and abutments, to implement effective scour countermeasures, and to deploy safety warning systems. The current instruments are not completely satisfactory in providing real-time monitoring data during critical flood events. This study introduces the development of an automatic scour monitoring system using time domain reflectometry (TDR) principle. It presents the principles and system design of the TDR sediment scour monitoring system. An analyses algorithm for scour signals has been developed. It was found to be robust and can be implemented to automate scour signal interpretation. Simulated experiments were conducted to validate the performance of the scour monitoring system prototype. The results showed that this TDR technology can accurately measure the scour depth. Besides, the properties of the sediments, such as the porosity and density can be estimated with reasonable accuracy. At the end of the paper, a few important issues associated with field deployments of TDR scour monitoring system are discussed.