SALT EFFECTS ON THE HYDRAULIC PROPERTIES OF A SWELLING SOIL

The effects of soil solution composition on the hydraulic conductivity (K) and the volumetric soil solution content were measured with mixed sodium chloride-calcium chloride solutions. The total electrolyte concentration (C) and the sodium absorption ratio (SAR) characterized the applied solutions. Steady-state flow cells were constructed with provision for (i) measurement of the volumetric flux of the solution phase during saturated and unsaturated flow conditions, (ii) measurement of the volumetric soil solution content by gamma attenuation, (iii) tensiometers for hydraulic gradient and pressure head (h) measurement, (iv) application of an external load on the soil, and (v) measurement of bulk volume changes. Soil samples were subjected to sequences of solutions varying in C from 1,000 meq/liter to 10 meq/liter at constant SAR values of 0, 5, 15, 25, and 40, respectively. Hydraulic conductivity decreases occurred during the first sequence of decreasing C at fixed SAR values equal to or greater than 5. The higher the SAR value, the greater the decrease in K with decreasing C. The K decreases occurred at all volumetric soil solution contents within the range of experimental data. Increases in volumetric soil solution content at given h values, and decreases in bulk density, occurred simultaneously with the decreases in K. Greater changes in K and volumetric soil solution content and smaller changes in bulk density occurred in the soil subjected to a higher external load. The K and bulk density decreases and the volumetric soil solution content increases were to a great extent irreversible, i.e. when C was subsequently increased at a fixed SAR value, K, bulk density and volumetric soil solution content did not regain their initial values. Substantial increases in K were obtained, however, if the soil was air dried, sieved, and repacked into the flow cell. /Author/

  • Supplemental Notes:
    • Proceedings of 42nd Annual Meeting, Chicago, Illinois, December 3-8, 1978.
  • Corporate Authors:

    Soil Science Society of America

    677 South Segoe Road
    Madison, WI  USA  53711
  • Authors:
    • Dane, J H
    • Klute, A
  • Publication Date: 1977-11

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Filing Info

  • Accession Number: 00173887
  • Record Type: Publication
  • Report/Paper Numbers: Proceeding
  • Files: TRIS
  • Created Date: May 31 1978 12:00AM