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South Dakota Department of Transportation
Project Synopsis
SD2004-02


Title: Corrosion Monitoring of Hot Springs VSL Mechanically Stabilized Earth Wall
Project Researcher: Dan Johnston, SDDOT
Project Manager: Daris Ormesher
Research Period: 4/1/2004 - 8/31/2006
Status:
Cost: $0.00

Problem Statement:Construction of a VSL Mechanically Stabilized Earth (MSE) Wall in Hot Springs was completed in 1983 to replace a 50 year old viaduct. The original system proposed for the wall, from the Reinforced Earth Company, was replaced on a value engineering basis by the VSL system, without the development of new construction plans. Numerous errors in construction, especially with regard to backfill compaction, resulted in a significant settlement at both abutments where the MSE wall transitioned into a structure. Fortunately, the settlement stabilized without compromising the integrity of the wall but, in the process, the PCC pavement placed atop the wall suffered severe cracking from the settlement. In addition, the contractor used backfill material from a pit different from the one originally approved for use, raising the question of potential corrosivity of the backfill material.

Since completion, a substantial amount of deicing and highway runoff has made its way into the wall through the pavement cracks and the current status of the galvanized reinforcing mats which provide stabilization is unknown. The PCC pavement is scheduled for replacement this summer and this construction will allow access to the top mats of reinforcement for evaluation. In addition, FHWAs Atlanta Resource Center has agreed to provide equipment and technical support for conducting a comprehensive evaluation of the corrosion situation within the wall at no additional cost to the Department beyond installing the access holes and instrumentation necessary to perform the evaluation and monitoring the corrosion environment of the wall reinforcement long enough to establish corrosion levels and predict their potential impacts.



Findings:
Title: Corrosion Monitoring of Hot Springs VSL Mechanically Stabilized Earth Wall
Project Researcher: Dan Johnston, DOT
Project Manager: Daris Ormesher
Research Period: 4/1/2004 - 8/31/2006
Status:
Cost: $0.00

Problem Statement:Construction of a VSL Mechanically Stabilized Earth (MSE) Wall in Hot Springs was completed in 1983 to replace a 50 year old viaduct. The original system proposed for the wall, from the Reinforced Earth Company, was replaced on a value engineering basis by the VSL system, without the development of new construction plans. Numerous errors in construction, especially with regard to backfill compaction, resulted in a significant settlement at both abutments where the MSE wall transitioned into a structure. Fortunately, the settlement stabilized without compromising the integrity of the wall but, in the process, the PCC pavement placed atop the wall suffered severe cracking from the settlement. In addition, the contractor used backfill material from a pit different from the one originally approved for use, raising the question of potential corrosivity of the backfill material.

Since completion, a substantial amount of deicing and highway runoff has made its way into the wall through the pavement cracks and the current status of the galvanized reinforcing mats which provide stabilization is unknown. The PCC pavement is scheduled for replacement this summer and this construction will allow access to the top mats of reinforcement for evaluation. In addition, FHWAs Atlanta Resource Center has agreed to provide equipment and technical support for conducting a comprehensive evaluation of the corrosion situation within the wall at no additional cost to the Department beyond installing the access holes and instrumentation necessary to perform the evaluation and monitoring the corrosion environment of the wall reinforcement long enough to establish corrosion levels and predict their potential impacts.



Findings:

Research Objectives:
1  Determine the corrosion condition of the Hot Springs VSL MSE wall.
2  Provide a long term assessment of the wall condition and its predicted performance and recommend repair and rehabilitation strategies based on the analysis.
3  Recommend procedures for instrumenting other MSE walls for corrosion monitoring.

Research Tasks:
1  Perform a literature search on the corrosion behavior and monitoring of metallic reinforcement elements in mechanically stabilized earth walls.
2  Meet with the technical panel and Rapid City Regional staff after inspecting the wall to discuss locations and installation of monitoring probes and necessary equipment and personnel needed to accomplish the task.
3  Install instrumentation within the wall at selected locations and establish a monitoring program to measure the extent and rates of corrosion on galvanized mat reinforcement.
4  Measure corrosion activity and visually appraise corrosion conditions in the top mat reinforcement after the contractor has removed the PCC pavement. Instrument the top mat reinforcement at locations corresponding to previously installed probes on th
5  Collect data using half cell potentials and polarization resistance measurements for a period suitable for establishing a stabilized corrosion assessment.
6  Analyze the data to determine the corrosion situations within various wall elements and any potential impacts to the performance or structural integrity of the wall.
7  Based on this assessment, provide recommendations for future repair, rehabilitation or replacement strategies for the Hot Springs Wall.
8  Evaluate the suitability of the corrosion monitoring procedures for retrofitting on other MSE walls or inclusion in new construction. Provide plan notes for new construction, if appropriate.
9  Prepare a final report of the literature review, research methodology, findings, conclusions, guidelines and recommendations.
10  Make an executive presentation to the SDDOT Research Review Board summarizing the findings and conclusions.

Documents Available:
SD2004_02_Final_Report.pdf
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