Bed – Structure System Analysis for Soil Freezing and Thawing Using the Termoground Program

Abstract

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.

Modern approaches to the design of bases and foundations at permafrost zone sites with account for the effects of global warming

“…Figure 7 shows the performance of heat stabilizers at the base. As can be seen from the figure, the calculated temperature fields at the base are close to those recorded experimentally, which indicates the correctness of the calculations (the calculations were performed using the Termoground software) [8]. Obviously, given the danger of global warming, the experience of the oil and gas industry can be used in industrial and civil construction in the North.…”

Stabilisation with geogrids for transport applications – selected issues

“…One of possible application which is not well verified is use of stabilizing geogrids in regions with soil freezing (Ulitskii et al, 2015). As shown on Fig. 14 installation of geogrid for stabilization reduced deflection of monitored section.…”

Thermal-physical calculations as a basis of design solutions of buildings and structures in the permafrost zone

“…Below there are some examples of solving the problems, which main feature is the thermal-physical component. To solve these problems we used the software "Termoground", which is renowned in the international practice, its principles and features are described in [1][2][3][4]. Calculations of pit fencing were made for active soil pressure caused by its dead load and a temporary load on the surface.…”