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Back-to-Back Mechanically Stabilized Earth Wall "To Grout or Not to Grout?"
A back-to-back mechanically stabilized earth (MSE) wall was constructed as part of the Hamilton Avenue Grade Separation for Santa Clara Valley Transportation Authority's (VTA) Vasona Light Rail Extension Project in Santa Clara County, California. Since completion of construction in July 2004, the back-to-back MSE Wall experienced settlement (150 to 200 mm or 6 to 8 inches) and lateral movement (50 to 100 mm or 2 to 4 inches), resulting in cracking of the wall panels and settlement of station platform, and requiring periodic ballast tamping to raise and realign the track bed. Two geotechnical consultants were retained by VTA to evaluate the wall settlement and to develop remedial measures to mitigate the continued movement. Both geotechnical consultants concluded that compaction grouting would be required to stabilize wall movement. Compaction grouting is expensive and would require the grouting work to be carried out at night and on weekends during non-revenue hours. There were also concerns about uneven lifting of the wall and the elevated station platform, and that grout might find its way into conduits and impact wires and cables Subsequently, VTA engaged a third consultant to provide an independent evaluation of the wall and to confirm that the grouting program offered the best investment of capital and maintenance funds. This study concluded that the wall movement was attributed to intrusion of water into the MSE wall. Sources of the water include a leaking underground valve, irrigation water for landscaping on the elevated platform, and steam cleaning/pressure washing of the station platform. Remedial measures consisting of surface and subsurface drainage were developed to improve the existing drainage systems, thereby eliminating the need for compaction grouting to stabilize the wall. This paper discusses the importance of determining the root causes of wall movement before implementing remedial measures. The lesson learned from this case study is "Do not rush to a solution before knowing the cause of the problem."
Back-to-Back Mechanically Stabilized Earth Wall "To Grout or Not to Grout?"
A back-to-back mechanically stabilized earth (MSE) wall was constructed as part of the Hamilton Avenue Grade Separation for Santa Clara Valley Transportation Authority's (VTA) Vasona Light Rail Extension Project in Santa Clara County, California. Since completion of construction in July 2004, the back-to-back MSE Wall experienced settlement (150 to 200 mm or 6 to 8 inches) and lateral movement (50 to 100 mm or 2 to 4 inches), resulting in cracking of the wall panels and settlement of station platform, and requiring periodic ballast tamping to raise and realign the track bed. Two geotechnical consultants were retained by VTA to evaluate the wall settlement and to develop remedial measures to mitigate the continued movement. Both geotechnical consultants concluded that compaction grouting would be required to stabilize wall movement. Compaction grouting is expensive and would require the grouting work to be carried out at night and on weekends during non-revenue hours. There were also concerns about uneven lifting of the wall and the elevated station platform, and that grout might find its way into conduits and impact wires and cables Subsequently, VTA engaged a third consultant to provide an independent evaluation of the wall and to confirm that the grouting program offered the best investment of capital and maintenance funds. This study concluded that the wall movement was attributed to intrusion of water into the MSE wall. Sources of the water include a leaking underground valve, irrigation water for landscaping on the elevated platform, and steam cleaning/pressure washing of the station platform. Remedial measures consisting of surface and subsurface drainage were developed to improve the existing drainage systems, thereby eliminating the need for compaction grouting to stabilize the wall. This paper discusses the importance of determining the root causes of wall movement before implementing remedial measures. The lesson learned from this case study is "Do not rush to a solution before knowing the cause of the problem."
Back-to-Back Mechanically Stabilized Earth Wall "To Grout or Not to Grout?"
Lee, Thomas S. (author) / Chirco, John (author) / Ilyas, Ehsan (author)
Geo-Congress 2013 ; 2013 ; San Diego, California, United States
Geo-Congress 2013 ; 505-514
2013-02-25
Conference paper
Electronic Resource
English
Back-to-Back Mechanically Stabilized Earth Wall ``To Grout or Not to Grout?''
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