Evaluation of Guidelines for Subgrade Treatment

The Ohio Department of Transportation has recently developed guidelines for subgrade treatments to be used during plan development and construction. This study evaluates these guidelines by comparing them with existing guidelines developed elsewhere and validating them through comparison of the actual treatment methods and quantities used with those suggested by the guidelines. Soil boring data and construction record from 7 reconstruction and 2 new construction projects were obtained. Actual treatment methods and quantities were obtained from the project field offices. Dynaflect deflection data, when available, were analyzed to determine their usefulness in subsurface assessments. "Geotechnical Bulletin GB1 on Plan Subgrades" criteria for excess moisture content predicted the undercut quantity reasonably well, but the criteria for acceptable moisture content tend to underpredict the undercut quantity in many cases, likely due to increased soil moisture content after removal of existing pavement. For reconstruction projects, the average undercut depths (i.e., the overall undercut quantities) versus the corresponding SPT N sub L values seem to fall reasonably well within the upper bound provided in the Section 204 guidelines. However, the actual undercut depths vary significantly even for soils with similar or same N sub L values. Actual undercut depth and quantity are somewhat correlated with the average SPT N sub L value, Dynaflect W5 deflection, and soil moisture content. The regression equation developed has a coefficient of determination (or R-squared value) as high as 0.71.

Language

  • English

Media Info

  • Media Type: Print
  • Edition: Final Report
  • Features: Appendices; Figures; Photos; Tables;
  • Pagination: 129p

Subject/Index Terms

Filing Info

  • Accession Number: 01001459
  • Record Type: Publication
  • Report/Paper Numbers: FHWA/OH-2005/003
  • Contract Numbers: State Job No. 147140
  • Files: TRIS, ATRI, USDOT, STATEDOT
  • Created Date: Jun 27 2005 11:08AM