Physical processes during freeze-thaw cycles in clayey silts

Abstract Repeated freezing and thawing affect the structure of clayey silts over a wide range of overconsolidation ratios. While the overall void ratio of the thawed soil may either increase, as in lightly over-consolidated soils, or decrease, as in heavily overconsolidated samples, freezing and thawing caused an increase in effective void ratio in all cases. This, in turn, led to a reduction in segregation potential after each freeze-thaw event and to an increase of vertical hydraulic conductivity of the thawed soil. All the changes occurred during the first three cycles. It was also inferred that no structural changes occurred in the frozen fringe but rather somewhere in the colder zone at a temperature between −0.40 and −0.57°C, dependent upon the overconsolidation ratio. A mechanistic model based on differential freezing in macro- and micro-pores of a clayey silt accounts for the experimental results.