Heave and Heaving Pressures in Frozen Soils

Most previous studies of frost heave and associated frost heaving pressures have been concerned with the process of ice lensing and ice segregation, and the primary mechanism used to explain the related phenomena of heave and pressure is seen to be consistent with the process of formation of ice lenses. Thus, while certain investigators may disagree on various details, there appears to be general agreement on the mechanisms which form the basis for the so-called capillary model for the prediction of frost heaving and associated pressures. In addition, various criteria used for the assessment of frost susceptibility rely implicitly on the admissibility of this model as their rationale.This study questions the advisability of using a singular capillary model, in view of the wide range of conditions and constraints prevailing at any one time. Since soil freezing involves moisture movement and associated resultant volumetric expansion at both the macroscopic and microscopic scale arising from temperature and osmotic gradients, it is clear that a comprehensive theory to rationally explain heave and (or) heaving pressures is needed to account for all major factors which influence the total response of the frozen soil system. In this respect, the results of a critical examination of recent field and laboratory tests performed at McGill University and elsewhere are used to show that the available theories may be too restricted in scope to explain all facets of the observed behavior of frozen natural soils. To overcome the shortcomings noted above, an extended generative mechanism is developed and procedures for the examination of actual results are presented.