Special Practices for Design and Construction of Subgrades in Poor, Wet, and/or Saturated Soil Conditions

Highway embankment construction progresses vertically in stages, beginning with the subgrade. For a variety of reasons, it is desirable to use naturally occurring soils for subgrade material. In some cases this is not possible due to poor soil conditions; in order to avoid realignment it is necessary to improve the subgrade material. A literature review provides background for special construction methods to be used for subgrade soil enhancement. Additonal information about modification, stabilization, reinforcement, and substitution methods and material was gathered from a questionnaire directed to Minnesota state, county, and city highway engineers. Based on questionnaire responses, a series of highway agency interviews were conducted to provide more detailed information about the enhancement methods. Enhancement selection recommendations and special practice methods for construction were developed from the agency interviews, questionnaire responses, and literature review.