United States Department of Transportation
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Edition:Final Report (2012-2018)
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Abstract:This report presents the findings associated with an effort to evaluate projects with weak subgrades utilizing the newly developed Equivalent Modulus Analysis (EMA) spreadsheet created by the Louisiana Department of Transportation and Development (DOTD). The EMA spreadsheet was developed to simplify the design process by allowing for easy application of the Method of Equivalent Thickness (MET) calculations that lies at the heart of the pavement design process. A validation was attempted by trying to compare the EMA spreadsheet’s predictions to field collected data. Lime treatment projects were used to do the assessment as lime treatment is often employed in establishing working tables for construction equipment that cannot operate on very weak subgrades. This research attempted to accomplish two objectives: (1) to try to find a way to incorporate lime treatments into the design process in order to take advantage of the strength it offers and (2) to explore the strengths and weaknesses of the MET approach used in the design process through utilization of the EMA spreadsheet to see if there is a way to assess weak subgrades. Results, however, were both inconclusive and questionable because the untreated and lime-treated soils typically sheared during field testing which invalidated back-calculation efforts. Additionally, it proved problematic to assume that raw subgrades could be held as two-layer systems in order to carry out back-calculation. As such, the EMA spreadsheet could not be validated. More testing would be required to validate the approach.
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