Abstract
The compression behaviour of a soil mass is influenced by freeze-thaw action, and the compressibility of thawy soil is larger than that of unfrozen one (Figs. 2-4). The cause appears to be that ice crystals are formed in the soil upon freezing. With the growth of the ice crystals, ice pressure acts on the unfrozen part, and with this, pore water moves to the crystals. Consequently, soil in contact with ice crystals will be subjected to three-dimensional consolidation. On the other hand, plastic deformation of the initial soil structure may be caused by transformation and movement of pore water in the system, so that pore water restrained by the structure becomes relatively free. Freezing temperatures, freeze-thaw repetition and the initial conditions of soil specimens determine the quantity, distribution, situation and form of ice crystals which are created in the soil mass. These in turn have an influence upon the compression-deformation behaviour of the thawy soil mass (Figs. 6-11).
If soil structure can be thought of as a graduated model, i. e. with fabric units: ped>cluster>domain, freezing effects will begin with the movement of peds, and, with increased intensity of freeze-thaw action, this will have a greater influence upon the unit itself or a smaller unit. From the above consideration, the increase in the components of secondary consolidation (Fig. 12) and the decrease in the restoration of strain with unloading (Figs. 13, 14) may be explained.
