Evaluation of a KeyStone/Tensar geogrid retaining wall system : final report.

PDFTech ReportExperimental Features Project No. OR 89-01Retaining wallsConcrete structuresGeogridsStructural designInstallationCost effectivenessDrainagePerformance evaluationsFootingsBlocksAestheticsPortland (Oregon)Oregon. Department of Transportation. Materials and Research SectionKliewer, Julia E.Yates, SteveBrooks, Eric W.Nodes, Scott E.Oregon. Department of Transportation. Materials and Research SectionUnited States. Federal Highway AdministrationUS Transportation CollectionThe KeyStone/Tensar Geogrid retaining wall system is an alternative to conventional reinforced concrete retaining wall structures. KeyStone concrete wall units, Tensar geogrid, and compacted soils are combined to form a reinforced soil mass that together act as a gravity wall structure to resist lateral earth pressures and surcharge loads.The objective of this experimental features project is to evaluate the construction and performance of the KeyStone/Tensar retaining wall system. The benefits, as stated by the manufacturer, of this wall system include: design flexibility, easy installation, cost efficient, beauty, and wall face drainage properties.The features of this wall system that were evaluated include: construction (including installation times and labor costs), quality and availability of precast elements, wall costs, aesthetics, wall stability and performance, and appropriateness of design details and parameters.Two walls located in Portland, Oregon were evaluated as part of this research. Wall 1 is approximately 183 feet long, facing Southwest Taylors Ferry Road. The wall has multiple footing steps to accommodate the roadway grade and ranges in height from approximately 2.5 feet to 16 feet. Wall 2 is approximately 190 feet long, fronting on Southwest Bertha Boulevard. The wall has one footing step to accommodate roadway grade and ranges in height from 2.5 feet to 6.5 feet.The KeyStone/Tensar geogrid retaining walls evaluated as part of this project have performed well for two years. Although problems were encountered with block placement during construction of the walls, these problems can be avoided in future projects by designing footing and block placement with consideration of horizontal growth, batter due to block setback and thickness of geogrid.Even though costs were not substantially lower than the estimate for conventional reinforced concrete retaining wall structures, the aesthetic qualities, performance, and construction time make this type of wall an acceptable alternative. Therefore, it is recommended that the KeyStone/Tensar Geogrid retaining wall system be considered as an acceptable alternative to conventional retaining walls for similar installations. Full acceptance of this retaining wall system for use on State projects will require completion of the OSHD Bridge Section's "Wall Acceptance Procedures;" these acceptance procedures are currently being developed