Fig. 2.8. Redistribution of moisture along the length of frozen samples (sample length h, mm, cm): a - as a result of shear in polymineral (1), kaolinite (2) and bentonite (3) clay (dashes show moisture prior to the experiment, arrows indicate the shear plane); b - in sandy-silty-clay after flow of electrical current.
Characteristics of moisture transfer and ice formation in frozen soils affected by gradients of mechanical stress, electricalfields and other external forces
Frozen soil masses have afield of mechanical stress gradients which originates and exists due to the natural and historical development of the soil and various engineering impacts. The difference of these stresses results in moisture migration from regions of higher to those of lower compressive pressures, from regions of lower to those of higher tensile or shear stresses. Widespread among the mechanical stresses arising in frozen ground are shear stresses. In the planes of shear, where the maximum stresses occur between soil particles with the minimum values of the thermodynamic potentials of moisture unfrozen water is under tensile stresses which result in its augmentation there under the effect of grad (Fig. 2.8a). Clearly, this process occurs particularly under slow shear lasting for days or months.
The layers away from the shear zone lose water. The remaking of the structure and formation of ice micro- and macro-streaks occurs in the shear zone (Fig. 2.9).
The density of flow of the unfrozen water Wun(, can be written as follows:
Was this article helpful?