The purpose of this study was to determine whether the Federal Aviation Administration (FAA) should retain its present soil classification system or change to another system. The study consisted of: A critical review of the American Association of State Highway and Transportation Officials (AASHTO), FAA, and Unified Soil Classification (USC) systems; A comparison of the merits of the FAA system with those of the other two systems; and an analysis of the possible impact on the airport pavement industry of any changes in the FAA system. Based on the analyses of the data, particularly the demonstrated levels of sensitivity of the three classification methods and the variability that exists in the field, it was recommended that the FAA adopt the USC system for the classification of soils. Pavement design based on soil classification has the disadvantages of not accounting for soil strength, compactibility, moisture content, and several other factors. This fact and the replies to the questionnaires lead to the recommendation that FAA develop new design procedures based on strength criteria. Classification would thus become a secondary, rather than a primary, factor in the design procedure. The implementation required for adopting the USC system should present no problems to FAA. The USC system has been in widespread use by engineers since the mid-1940s. Engineering colleges with accredited courses in soil mechanics teach the method routinely. Soils and paving engineers have been using the method for more than 20 years, and there should be no difficulty in adapting to it. In fact, the replies to the questionnaires suggest that many engineers are looking forward to the change, should it be made. /Author/

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    • This paper appeared in TRB Special Report 175, Research in Airport Pavements. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
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    Transportation Research Board

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  • Authors:
    • Horn, Frederick
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  • Publication Date: 1978

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  • Media Type: Print
  • Features: References;
  • Pagination: pp 60-61
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Filing Info

  • Accession Number: 00189931
  • Record Type: Publication
  • Files: TRIS, TRB, ATRI
  • Created Date: May 11 1979 12:00AM