Bridge Scour Monitoring
A National Science Foundation and U.S. Army Corp of Engineers funded project.
Project title: Scour Monitoring and Failure Prediction for Safe and Resilient Transportation Infrastructures
Source of support: National Science Foundation and U.S. Army Corp of Engineers
Scour monitoring can prevent scour-induced damage and failure of overwater bridges. Two novel scour sensing techniques with the potential for continuous and robust monitoring during flood events are proposed. First, a small-scale piezoelectric rod functioning based on the concept of a vibrating cantilever beam is designed, fabricated, and calibrated (Fig. 1). A piezoelectric thin film was embedded in a rod, and the scour sensor rod was buried beneath the bed. When scour erodes soil and sediments near the vicinity of the buried rod, flow would induce vibrations of the buried rod and piezoelectric sensing element. By monitoring the generated voltages and by extracting the characteristic vibration properties of the buried rod, the exposed length (or equivalently scour depth) was be determined. Laboratory-scale validation tests were performed in which a network of these buried rods were installed. Fig. 2 shows a representative result that compares the results obtained from the prototype buried scour sensing rod and against manual measurements of scour depth throughout the entire duration of a test.
The second sensing system utilizes commercially available miniature dissolved oxygen (DO) probes (Fig. 3). DO probes operate as scour sensors due to a pronounced difference between the oxygen levels in the riverbed and flowing water. Both sensing techniques were examined when deployed as arrays around a small-scale bridge pier in flume tests. It was demonstrated that both sensors can detect scour as it occurs and continue to function as soil is redeposited in the scour hole (Fig. 4). Ongoing research is aimed at creating a practical cost-value framework for scour sensor selection and interpretation.
Read more about this topic in an article published in The Economist.
- Prof. Michael Todd, UC San Diego
- Prof. Chin-Hsiung Loh, UC San Diego
- Elintrix (Escondido, CA)
- F. Azhari and K. J. Loh, 2016, "Laboratory Validation of Buried Piezoelectric Scour Sensing Rods," Journal of Structural Control and Health Monitoring (1545-2263), Wiley. DOI: 10.1002/stc.1969
- F. Azhari and K. J. Loh, 2016, "Dissolved Oxygen Sensors for Scour Monitoring," IEEE Sensors (1530-437X), IEEE, 16(23): 8357-8358. DOI: 10.1109/JSEN.2016.2613123
- F. Azhari, P. Scheel, and K. J. Loh, 2015, “Monitoring Bridge Scour using Dissolved Oxygen Probes,” Structural Monitoring and Maintenance (2288-6605), Techno-Press, 2(2): 145-164. DOI: http://dx.doi.org/10.12989/smm.2015.2.2.145
- K. J. Loh, C. Tom, J. Benassini, and F. Bombardelli, 2014, “A Distributed Piezo-polymer Scour Net for Bridge Scour Hole Topography Monitoring,” Structural Monitoring and Maintenance (2288-6605), Techno-Press, 1(2): 183-195. DOI: 10.12989/smm.2014.1.2.183
Fig. 1: Buried cantilevered piezoelectric scour sensors are excited by ambient flowing water, and their dynamic properties vary depending on their exposed lengths (scour depth).
Fig. 3: Dissolved oxygen sensors are buried along a bridge pier, and drastic changes in DO levels indicate their exposure to ambient water due to scour.
Fig. 2: Buried piezoelectric scour sensors only required a single voltage measurement, and the raw data could be processed to obtain scour depths that coincided well with manual measurements obtained during a flume test.
Fig. 4: Miniature DO sensors were embedded at different depths at one particular location during a flume test. The results showed that the measured dissolved oxygen content changed dramatically as soon as scour progressed to the depth of the sensor to expose them to flowing water of higher DO content.
(C) Copyright 2018 UC San Diego and Prof. Ken Loh. All rights reserved.