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Several laboratory studies have shown that the hydraulic conductivity of compacted clay may increase up to three orders of magnitude when subjected to freeze-thaw. In this paper, methods to freeze and thaw specimens of compacted clay are reviewed and compared. Methods to measure the hydraulic conductivity of the specimens are also reviewed. Only naturally formed clay soils are considered; soil-bentonite mixtures and other amended soils are not included.
A review of testing conditions present during freeze-thaw and their effect on hydraulic conductivity is also included. Testing conditions that are addressed include availability of an external supply of water (closed vs. open system), dimensionality of freezing (one-dimensional vs. three-dimensional), rate of freezing, ultimate temperature, number of freeze-thaw cycles, and state of stress. The rate of freezing, number of freeze-thaw cycles, and state of stress appear to have the largest effect on hydraulic conductivity.
The effect of sampling disturbance on the hydraulic conductivity of compacted clay subjected to freeze-thaw is also presented. Specimens removed in Shelby tubes may be disturbed during sampling and extrusion. As a result, the effects of freeze-thaw can be masked. Collecting block specimens of thawed clay or taking core specimens of frozen clay are suggested as alternative procedures. A method to collect block specimens is presented.
freeze-thaw, compacted clay, hydraulic conductivity, consolidometer, permeameter
Assistant Project Engineer, GeoSyntec Consultants, Atlanta, GA
Assistant Professor, University of Wisconsin, Madison, WI
Research Civil Engineer, U. S. Army Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire
Associate Professor, Rensselaer Polytechnic Institute, TroyNew York,