The means of controlling the stability of engineering structures in the permafrost regions, methods of modification for frozen, thawing and unfrozen soils and ways of site preparation are discussed. Evaluation methods of thermal and mechanical interaction between structures and soils of bases are presented. The scientific basis of optimizing engineering choices on the base of geotechnical systems reliability and cost optimization are given. Interaction of buildings and structures are analyzed.

Variations in the bearing capacity of permafrost beds beneath engineering structures in the course of naturalhistorical evolution of the natural setting are evaluated, and recommendations are given for accounting for these variations in design. The paper is written on the basis of results of studies financed by the Russian Fund for Fundamental Research (Project No. 94-05-16195-a).As we know, the strength of frozen soils, which determines the bearing capacity of beds, depends heavily on the value of their negative temperature, which depends, in turn, on the climate and heat exchange on the daylight surface. The ambient-air temperature and the depth of the snow cover, which, as observations indicate, undergo significant variations during the course of the natural-historical evolution of the natural setting, are primary climatic parameters that define the temperature of permafrost. According to multiyear meteorological observations in northwestern Siberia, the amplitude of fluctuations in the mean-annual air temperature is 2~ and the maximum depth of snow cover is tm. These significant variations in climatic parameters will certainly also lead to variations in the bearing capacity of beds. For a quantitative estimate of these variations, we selected two meteorological stations, one of which (Marresale) is located in a region with low-temperature frozen strata, and the other (Salekhard) in a region with high-temperature frozen strata. The observational period was 24 and 52 years for the first and second stations, respectively (Fig. 1). The temperatures of the permafrost at a depth of 10 m, which are used hereinafter to determine the bearing capacity of reinforced-concrete piles 0.3 x 0.3 m in section and 10 m long for beds of supports for transmission lines, antenna-tower structures, and pipelines, were calculated on the basis of data obtained by the method of mathematical modeling in accordance with the program "WARM." The bearing capacity was determined in conformity with recommendations set forth in Construction Rules and Regulations 2.02.04-88. In that case, heavily iced clayey foams that are highly prevalent in the Marresale region were adopted for it as bed soil, while slightly iced sands and sandy loams were taken for the Salekhard region. The temperatures and bearing capacities calculated for the permafrost (Fig. 2) suggest that the soil temperature at a depth of I0 m fluctuates from -3.6 to -7.3 ~ (Marresale) and from -0.4 to -3.0~ (Salekhard) as a result of the natural-historical evolution of the natural setting. A change in bearing capacity from 2400 to 3100 kN (Marresale) and from 360 to 2256 kN (Salekhard) corresponds to this temperature variation. Thus, the range in bearing capacity differs significantly for approximately the same range in temperatures of the soil. It is 102% of the minimum bearing capacity in the region of low-temperature permafrost and 525% in the region of high-temperature permafrost. This significant reduction in bearing capacity will inevitably lead to the deformation of structures...

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