Impact of Severe Drought on the Compacted Expansive Clays (Subgrade) in Northern Louisiana

In northwestern Louisiana, most of the subsurface soils (down to a depth of 20 feet) are mainly stiff red, gray and brown fat clay known as expansive soil. Its large volume change could trigger large, deep cracks in dry weather. The high shrink-swell property can cause serious damage to foundations and highways. The issue has not been well addressed in Louisiana. The purpose of this study is to develop a clear understanding of the fundamental volume change behaviors of compacted expansive clays in Louisiana, with a focus on severe drought conditions. Geotechnical index properties will be determined for preliminary soil assessment. Soil water characteristics curve (SWCC) will be plotted to understand the water retention capacity of the clay. Similarly, the shrinkage path and the swelling potential will be determined to study soil volume changes during shrinking and swelling, respectively. In the laboratory test, the swell-consolidation test will be conducted to determine the swelling pressure and to predict heave or settlement. Among these commonly used empirical equations, one or two ground heave/settlement prediction equations will be recommended for pavement design use in Louisiana. The mechanism of longitudinal crack developed at the pavement surface caused by expansive soils will be investigated. Finite element method will be utilized to establish a model to analyze the longitudinal crack mechanism by taking into account the volume change of subgrade, interaction between pavement structure and soil. In the model, pavement, shoulder, edge-drain, base, subbase, subgrade and natural embankment will be modeled in different constitutive descriptions. Additionally, cement, lime or/and fly ash treated expansive clays in northern Louisiana will be evaluated through swelling and shrinkage tests. Improvement in subgrade shrinkage and cracking will be studied based upon key factors such as stabilized (cement, lime or fly ash) content, material type, density, pre-treatment moisture content, molding moisture content, curing time and compaction method. The research will advance in-depth understanding of the volume change properties of the expansive clays.


    • English


    • Status: Active
    • Contract Numbers:


      SPTC 14.1-76

    • Sponsor Organizations:

      Louisiana Tech University

      P.O. Box 10348
      600 Dan Reneau Drive
      Ruston, Louisiana  United States  71272-0046

      Research and Innovative Technology Administration

      University Transportation Centers Program
      1200 New Jersey Avenue
      Washington, DC  United States  20590
    • Performing Organizations:

      Louisiana Tech University

      P.O. Box 10348
      600 Dan Reneau Drive
      Ruston, Louisiana  United States  71272-0046
    • Principal Investigators:

      Wang, Jay

    • Start Date: 20140801
    • Expected Completion Date: 0
    • Actual Completion Date: 20160731
    • Source Data: RiP Project 37452

    Subject/Index Terms

    Filing Info

    • Accession Number: 01543095
    • Record Type: Research project
    • Source Agency: Southern Plains Transportation Center
    • Contract Numbers: DTRT13-G-UTC36, SPTC 14.1-76
    • Files: UTC, RiP
    • Created Date: Nov 5 2014 1:01AM