EFFECTS OF FREEZING ON HYDRAULIC CONDUCTIVITY OF COMPACTED CLAY

A compacted clay is subjected to five cycles of freezing and thawing at constant water content. The test specimens are then permeated in flexible-wall permeameters at a relatively low effective stress of 35 kPa (5 Psi) to determine the effect of freeze-thaw on hydraulic conductivity. For soil compacted dry of optimum. hydraulic conductivity after freezing is two to six times larger than before freezing. For soil compacted wet of optimum, hydraulic conductivity increases approximately 100-fold. Susceptibility to freeze-thaw damage is found to be insensitive to compactive effort; soils compacted with modified compactive effort are no more resistant to freeze-thaw damage than soils compacted with standard effort. Freezing changes the void ratio, structure, and fabric of the soil, which in turn produces increases in hydraulic conductivity. These findings are consistent with other information reported in the literature and indicate that compacted clay subjected to low effective confining stress should not be allowed to freeze if low hydraulic conductivity must be maintained.