Vestnik MGTU (Apr 2020)
Assessment of the efficiency of passive thermal protection system of rock massif
Abstract
The problem of ensuring the stability of rock mass is of particular importance in the conditions of thermal interaction of mine workings with permafrost rocks. The paper presents the results of studying the effectiveness of passive thermal protection system of permafrost massif. Based on a numerical modeling by use of ANSYS FLUENT software complex, studies of thermal interaction of a large-span chamber working and permafrost massif have been performed. On the example of a hypothetical three-dimensional model of mine working with different variations in the material composition of the protective structure (lining) of working and the use of convective heat transfer in the technological channel (air gap), it has been performed the calculated study of the features of the temperature regime of the lining structural elements. There has been carried the estimation of the predicted depth of thawing of rock depending on the design and material composition of the lining and the duration of the thermal impact on the rock massif. The influence of the thermal resistance of the mine working protective structure on the depth and dynamics of thawing rock massif has been studied, the structure determines the conditions of preservation of its cryogenic state and requirements for mining systems of regulation of the thermal regime. The temperature gradients formed in the structural elements of the lining, which can contribute to the occurrence of thermal stresses that have a negative impact on the stress-strain state of the protective structure of the mine working have been founded. On the example of the accepted model representations of the technological channel (temperature of the entering air, width of the channel) the weak influence of heat exchange due to free convection on the intensity of thermal interaction of the working and rock massif has been shown. To reduce the thermal impact on the protective structure of the mine working and the permafrost massif it is necessary to increase the intensity of heat exchange in the technological channel by decreasing the temperature of the air entering the channel, or using the forced convection based on the organization of a special ventilation system.
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