American Society of Civil Engineers

Swell versus Saturation for Compacted Clay

by Robert W. Day, M.ASCE, (Chief Engr., American Geotech., 5764 Pacific Center Blvd., Suite 112, San Diego, CA 92121)

Journal of Geotechnical Engineering
, Vol. 118, No. 8, August 1992, pp. 1272-1278, (doi:

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Document type: Technical Note
Discussion: by D. R. Phatak and et al.    (See full record)
Closure:(See full record)
Abstract: The purpose of this study is to investigate the relationship between swell and degree of saturation for a compacted clay. Laboratory tests indicate that the percent swell increases in direct proportion to the degree of saturation at the end of the test. The linear relationship does not intercept the initial compacted degree of saturation. The coefficient of swell can be affected by the compacted effort. The dry, hard clods are broken down by the higher compactive effort. This reduction in interclod voids probably causes the significantly different coefficient of swell. Swell tests compacted to low, dry densities have a final saturation degree below 90%, even after two cycles of secondary swell. This indicates the presence of entrapped air. The main factor governing entrapped air for this soil appears to be the initial compacted void ratio. By itself, the degree of saturation does not seem to reliably indicate future potential for swell. One problem is the presence of entrapped air, which can result in a saturation degree below 90%, even when the sample has essentially stopped swelling.

ASCE Subject Headings:
Expansive soils
Swelling (material)
Volume change