Abstract
The changes of soil-mass behaviour with freezing and thawing cause basic changes in the soil structure. These changes are controlled by ice crystalization in the soil-mass. The fundamental patterns of the structural changes are shrinkage of the fabric units, formation of large pores among the units and increased pore-size distribution.
In this study, the above influences were investigated according to the soil-mass conditions.
1) Soil water conditions upon freezing were controlled in 9 stages from pF 0.6 to 2.5, and the effects produced by this treatment were examined (Figs. 3-5). The following conclusions were reached from the results. In the case of higher pF range, the external pore size of units increases with the freeze-thaw process, but is relatively uniform. On the other hand, with a lower pF range, the pore size is distributed more widely and also contains macro-pores (Figs. 11, 12).
2) The degree of freeze-thawing effects differs according to the type of soil (Figs. 6, 7). LL, indicating the condition of the soil-water system, is used to mutually compare the above effects. Soils of lower LL, even if they are similar clayey soils, show a relatively large structural change due to freezing.
In the case of silt, Ho, its behaviour is different from clayey soils due to the difference in the nature of the fabric units (Figs. 8, 9, 13, 14).
3) Effects of the original structure were examined by comparing undisturbed and disturbed specimens of the same soil (Fig. 10). At a higher pF range within the pore water retentivity, the two showed different tendencies. Namely, there was no significant change in water retentivity for the undisturbed specimen, but there were clear decreases for the disturbed one (Figs. 15, 16). From these results, it is considered that ice crystals grow more easily by destruction of the original structure.
