DOI: 10.25136/2409-7543.2022.4.38938

Abstract: The thermal regime of underground cryolithozone structures for various purposes, both related and not related to mining production, is an important factor determining their reliable and safe operation. In this regard, the forecast of the thermal regime in mine workings is a mandatory and important element in the justification of design solutions for the construction and reconstruction of underground structures in the areas of distribution of continuous and island permafrost. One of the main sources of heat generation in the workings is the work of diesel equipment, which is widely used, both in the development of mineral deposits by the underground method, and to ensure technological processes in underground structures of non-mining profile. The purpose of the research was to quantitatively assess the effect of diesel installations on the thermal regime in the underground structures of the cryolithozone. The results of numerical calculations are presented in the form of 2D and 3D graphs, which allow you to visually assess the effect of diesel equipment on the increment of air temperature in the underground structure, depending on the time of year and the efficiency of the diesel installation. It is shown, in particular, that in the most probable range of changes in the efficiency of a diesel installation, the air temperature can vary from 3.2 to 6.3 °C, depending on the standard values of the ventilation air flow. It is established that the temperature increment does not depend on the number of simultaneously operating diesel units and is determined only by the specific standard air flow (m3 / s per 1 kW of installation power).

DOI: 10.7256/2453-8922.2022.4.39349

Abstract: When designing cryolithozone engineering structures, proper consideration of the thermal factor largely determines their subsequent reliable and safe operation. One of the important indicators when choosing design solutions is the coefficient of thermal conductivity of materials used in the construction of objects. The accuracy of determining the thermal conductivity coefficient also depends on the accuracy of determining the thermal resistance of heat-protective structures. The coefficient of thermal conductivity of materials is usually selected from the reference tables. When using mixtures of materials, the coefficient of thermal conductivity is determined by calculation. The purpose of this work was to compare the calculated values of the thermal conductivity coefficient of binary mixtures (a mixture of binder and filler) determined by the formulas of K. Lichtenecker and P. Schwerdtfeger. The comparison was carried out in the range of changes in the properties of materials characteristic of heat-accumulating and heat-insulating mixtures. It is established that for heat-accumulating mixtures, both calculation formulas give similar results. For thermal insulation mixtures, the results differ significantly. Moreover, the discrepancy for some ranges of changes in filler concentrations is hundreds and thousands of percent, which indicates a complete disagreement of the results obtained. The validity of applying one or another formula in different ranges of changes in the initial parameters for thermal insulation binary mixtures needs separate special studies. Note that the results obtained and the conclusions drawn can be extended to compare the formulas of K.Lichteneker and V.I.Odelevsky. At the same time, at this stage of research, it is not possible to reliably determine which of the two formulas should be used when calculating the thermal conductivity coefficient of thermal insulation mixtures.

DOI: 10.7256/2453-8922.2022.2.38103

Abstract: One of the important parameters determining technical solutions in the design of highways in the cryolithozone is the depth of thawing of the soils of the road base. The aim of the work was to quantify the degree of influence of the iciness of the soil foundations of roads in the cryolithozone on the depth of their seasonal thawing. For the analysis, the classical formula for calculating the thawing depth for bodies of plane symmetry, obtained by solving the single-phase Stefan problem, was used. The results of calculations are presented in the form of 2D and 3D graphs, which allow us to visually assess the effect of the iciness of the soil and the degree of its change during the operation of the road on the depth of thawing of the road base. It was found, in particular, that the degree of change in the depth of thawing at the same value of the increase in ice content in different ranges (for example, from 10 to 20% and from 30 to 40%) for the considered typical case of the ground base of the cryolithozone decreases by almost 1.3 times. It is shown that the greater the initial iciness of the soil, the degree of decrease in the depth of thawing when the iciness changes by a constant value will be less. A 3D graph was built to determine the depth of thawing of the soils of the active layer of the road base in a wide range of possible changes in ice content during the construction and use of the highway. The availability of a schedule allows to quickly assess possible options for changing the depth of thawing and make a correct, informed technical decision when designing the road. For example, when assessing the need to use a special heat-protective layer in road clothing. Further directions of research in this area should be aimed at studying the effect of humidity (iciness) of dispersed soils on the depth of thawing of road foundations, taking into account the dependence of the density and thermal conductivity of the soil on the iciness.