Laboratory Characterization of Fine-Grained Soils for Pavement ME Design Implementation in Idaho

The subgrade layer often represents the weakest component of a pavement system, and can significantly affect pavement response and performance under loading. Adequate characterization of subgrade properties is critical to the design and construction of long-lasting, economical pavement systems. The Mechanistic-Empirical (M-E) pavement design protocol implemented through AASHTOWare Pavement ME Design requires resilient modulus of the subgrade soil as one of the primary input parameters. However, performing repeated load triaxial tests to establish the resilient modulus properties of soils is a cumbersome task, and is rarely undertaken by state transportation agencies on a regular basis. The Idaho Transportation Department (ITD) has recently invested significant amount of time and resources to facilitate state-wide implementation of M-E pavement design practices. This study was recently undertaken to characterize typical subgrade soils in Idaho. Extensive laboratory characterization of the soils was carried out including repeated load triaxial testing for determining the resilient modulus values. Several different pavement sections were analyzed by using currently used default values and laboratory-established soil properties as subgrade layer inputs during M-E design. Currently used default soil modulus values were found to be significantly higher than laboratory-established values, and therefore, resulted in the design of pavement sections that would fail considerably early into their service lives. The effect of moisture content on subgrade soil properties was also studied, and the importance of restricting soil moisture contents to the dry side of optimum was highlighted.


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  • Accession Number: 01747944
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jun 30 2020 3:05PM