EVALUATION OF LABORATORY SUCTION TESTS FOR PREDICTION OF HEAVE IN FOUNDATION SOILS

Commonly used methods for determining swell potential and predicting volume change and in situ heave are evaluated from the standpoint of simplicity, economy, reliability of test data, and simulation of field conditions. Swell potential is often defined as the percent swell from in situ water content to saturation under a surcharge pressure of 1 psi, whereas in situ heave is often defined as the percent swell from changes in the initial to assumed equilibrium moisture and confining conditions in the field. Increasing degrees of expansion or swell potentials usually correlate with increasing liquid limits and plasticity indices. Methods for determining swell pressure and predicting in situ volume changes or heave often use results of swell tests performed on undisturbed samples in the lD consolidation apparatus. A new method for determining swell potential and predicting in situ volume changes based on soil suction relation ships is described herein. The suction method is simple, takes little time, requires inexpensive equipment, and may simulate important field conditions including effects of lateral pressure and mechanics of the heaving process more closely than swell tests. The equation for determining swell pressure by the suction method is consistent with the results of previous research; the swell pressure is primarily a function of the dry density for a given soil. Comparisons of results of tests performed on undisturbed samples indicate that swell pressures computed by the suction method and denoted herein as suction swell pressures are similar to swell pressures measured from swell tests. The amount of swell pressure depends on the type of swell tests. The equation for determining volume changes and heave in soils by the suction method is consistent with the consolidation equation for calculation of settlements. Swell indices computed by the suction method are usually larger than swell indices measured from most swell tests. Predictions of volume changes and heave computed by the suction method may consequently be greater than those computed by other methods using results of most swell tests assuming identical equilibrium mositure and confining conditions. The suction index may also be used as an estimate of the relative degree of expansion of soils. For special cases in which the degree of saturation is one, the suction index approaches the magnitude of the compression index and can be used as an estimate of the compression index. /Author/

  • Corporate Authors:

    U.S. Army Waterways Experiment Station

    3909 Halls Ferry Road
    Vicksburg, MS  USA  39180-6199
  • Authors:
    • Johnson, L D
  • Publication Date: 1977-8

Media Info

  • Features: Appendices; Figures; References; Tables;
  • Pagination: 92 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00164082
  • Record Type: Publication
  • Report/Paper Numbers: Tech. Report S-77-7 Final Rpt.
  • Files: TRIS, ATRI
  • Created Date: Nov 9 1977 12:00AM