A number of complex problems arise when planning and managing land use in areas of extensive permafrost and regions of deep seasonal freezing, where intensive construction of ports, oil-and-gas facilities, railroads, and highways is planned over the next few years.Freezing and thawing soil may occur in structure beds, come into contact with vertical or inclined walls (excavation shoring, retaining walls), or surround structures (an ice layer in tunnels). One way or another, freezing and thawing processes accompanied by volumetric changes have a significant influence on the stress-strain state of a structure-soil system, which must be considered in analyses.However, even the one-dimensional Stefan problem, where the frozen and unfrozen portions are divided by a clear boundary with a phase transition temperature of 0°C, is nonlinear. In clays containing bound water, consideration must be given to phase changes into the so-called "spectrum of negative temperatures," which results in additional complexity of analysis. When two-and three-dimensional problems of this kind must be solved, only the use of numerical methods is feasible.Rigorous solutions are as yet not possible for evaluating the deformations that develop when soil freezes. Multiple experiments suggest that heaving deformations depend on many factors. It may be stated that migration of moisture to the frost boundary, which contributes significantly to heaving deformation, is occasioned by the combined action of surface and volumetric forces. However the authors are aware of no adequate quantitative description of this process with sound theoretical approaches.Thawing deformations are determined fairly simply, and the procedure for analyzing them, based on the work by G. I. Lapkin and N. A. Tsytovich, may be taken as a baseline. At the same time, however, it is worth noting that the use of the well-known factors A and m (defining settling due to heat and load, respectively), which are obtained under conditions of compressive compaction, are not entirely correct when analyzing three-dimensional problems.From what has been stated, it is clear that thermophysical and deformation problems of soil freezing and thawing are extremely complex. They may be solved as follows.A description is presented for a mathematical model to determine temperature patterns in structure beds that consider phase transitions in soil moisture, as well as the stress-strain state of soil over the course of freezing and thawing. Analysis examples are considered for various permafrost occurrence conditions and temperature exposures.
