Time Domain Reflectometry for Automatic Bridge Scour Monitoring

Abstract

Scour poses severe threat to bridge service conditions. The function of bridge piers and abutments might be significantly impaired due to extensive scour. Field monitoring of the scour process is important for studying scour mechanism, improving pier design, planning effective remediation measures, and deploying emergency warning systems. The current tools for bridge scour monitoring are generally not satisfactory for these purposes. This paper introduces an automatic scour monitoring system using Time Domain Reflectometry principle. The TDR sensor probe was designed by Yankielun and Zabilansky. Experience indicated that some TDR systems are sufficiently rugged for field installation and monitoring. This paper discusses the efforts toward developing a fully automatic scour monitoring system. An algorithm was developed to systematically interpret TDR signals by understanding the electromagnetic wave phenomena and TDR system characteristics. The performance is evaluated by analyzing the data obtained from a laboratory experiment. Results indicate that the algorithm accurately determines the thickness of sedimentation. In addition, the TDR scour monitoring system provides real time estimation of sediment physical condition including the water content and density. The system will be a valuable tool for investigating bridge scour mechanism and will have important engineering application potentials.