The objective of this project is to use advanced sonar technology for identifying and monitoring the problem of scour around bridge piers. As a rapid assessment tool, this can aid and sometimes replace physical inspection by divers. This will also provide some practical constraints and limits on the scour prediction models. We will consult with RIDOT and USACOE to identify critical areas of study. Potential candidates for this study could be Sakonnet Bridge, Washington Bridge Project and Jamestown/ Newport Bridges. Specific objectives that will be addressed in this project include
1.Investigate the various scour prediction models and their applicability to local conditions.
2.Collect field measurements using a number of advanced acoustic instruments and techniques (forward looking sonar, downward looking sonars etc.). In addition other environmental measurements (current measurements) will also be taken.
3.Calibrate the models using the field measurements taken.
4.Investigate the effectiveness of acoustic measuring techniques as a rapid assessment tool.
Highway
Riverbed scour near bridge piers is a widespread problem which causes scour holes to develop, piers to fall and, ultimately, bridges to collapse. Measurement of riverbed scour and deposition near bridge piers are essential for the proper maintenance and safety of bridges. Scour processes have been extensively studied and mathematical models have been developed from physical models and field data. But scour depths predicted using these models could vary substantially when these models are applied outside the range of conditions for which they have been developed. Field measurements of scour depths are needed to put practical constraints and limits on these models. We will conduct these field measurements using a number of underwater acoustic instruments and techniques. These instruments include depth sounder, side scan sonar, sub-bottom profiler. These measurements will be conducted aboard the Department of Ocean Engineering research vessel R/V CT-1 or similar research vessel. This will also then serve as a rapid assessment tool for scour and has the potential to compliment and/or replace inspection by divers.
1. Literature review of the scour prediction models. Some of the information has already been collected.
2. Identify bridges where scour may be present. Input from RIDOT and other consultants involved will be solicited.
3. Field data collection using current meter, depth sounders, side scan sonars and sub-bottom profiler. The department vessel R/V CT-1 or a similar research vessel will be used for data collection.
4. Analysis of the data and correlation with scour models. The scour depths measured will be correlated with predictions from scour prediction models.
5. Progress reports and final report. Progress reports will be submitted to URITC on a quarterly basis in addition to the final report.
Tasks 1 and 2 will be carried out simultaneously during the months of May-July, 2003. Initial fieldwork will be conducted during the month of August 2003. Preliminary analysis of the results will be done during September, 2003. Based on this initial fieldwork, necessary modifications will be carried out to the field program. The full fieldwork will be then carried out during October, 2003- January, 2004. Analysis of this data will be carried out in February- March 2004. Last month (April, 2004) will be devoted to final report preparation.
$115,592.00 ($115,592.00 Yearly)
One PhD student will be working on this project
In addition to the direct application to bridge scour monitoring, this study will also provide field data for research into estimation of geoacoustic properties of sediments. The Department of Ocean Engineering has an active research program addressing this research area. Advanced signal processing methods have been developed to analyze broadband signals at low frequencies. Indirect bottom survey methods using acoustic propagation which are fast and cover large areas have been also been developed. These techniques can be extended for application to these field measurements obtained at higher frequencies. Thus there is potential for indirect benefits from this study to advanced research in sediment tomography.
The results of this research will be presented as a report to URITC at the end of the study. Findings also will be presented in conferences and published in literature.
This project will identify the extent of the problem scour in the area bridges and develop a scheme for monitoring scour. The method has the potential as a rapid scour assessment tool.
Scour at bridges, sonar, acoustic monitoring, scour prediction, bridge safety