Nanotechnology and parameters of permafrost soil thawing in the construction of building foundations and transportation structures

Introduction. The construction of infrastructure facilities, industrial enterprises and residential complexes requires design solutions that ensure the operational reliability of foundations in conditions of degradation of permafrost groundwater. The geological conditions of permafrost soils affect the strength, stability and durability of structures. Construction without taking into account the characteristics of permafrost soils leads to precipitation; deformations of buildings and emergency situations associated with the degradation of the soil mass due to changes in climatic conditions. Existing technologies may not always meet the requirements for the reliability of construction facilities. In order to maintain the durability and stability of structures, it is necessary to take into account risk factors for the northern regions, where climatic conditions are very harsh and construction sites are subjected to significant loads. Rising average annual air temperatures are causing the active layer–the seasonally thawed portion of permafrost soils–to deepen across all affected regions. When designing modern structures, the depth of foundation must be increased, which in turn leads to an increase in construction costs in permafrost zones. Based on the results of the calculation, the required temperature of steam supply to the steam needle, the diameter of the needle, the thickness of its wall, the arrangement of needles, the area of thawing from both one and a complex of steam needles, as well as the time of back-freezing of the soil mass were determined to take into account the possibility of work on their fastening. Materials and methods. The article presents the nanotechnology of thawing permafrost soils with steam needles and the calculation justification necessary to take into account the possibility of work on thawing the soil mass and their further consolidation. The calculation justification is based on the example of the construction of a transport facility in Norilsk, Krasnoyarsk Territory, since this region belongs to the regions of the Far North. The calculation was performed in the specialized software package MIDAS GTS NX Thermal analysis. Discussion. The following was performed: verification of the calculation models; simulation of the existing range of steam needle wall thicknesses; simulation of the existing range of steam needle diameters; simulation of the existing temperature range of steam supply to the steam needle; modeling of two possible schemes for the placement of steam needles in a soil array; modeling to determine the distance between steam needles when they are installed in an array of soils; modeling to determine the time required for the thawing of the soil mass and their reverse cooling. The analysis of the results is performed for each of the stages of the calculation justification. The optimal design of the steam needle (diameter, wall thickness, steam supply temperature), the arrangement of the needles and the distance between the needles when they are installed in the soil array, the area and volume of the heated soil array, the time of thawing and reverse cooling of the soil array are determined. Conclusion. As part of the work performed, the design parameters of the steam needle are justified, including the optimal diameter, wall thickness and temperature of the supplied steam. The optimal location of steam needles and the necessary distances between them have been established, key indicators of the process of thawing permafrost soil have been determined: the timing, volume and area of thawing, as well as the time interval for the return of soils to their original frozen state. The results of the presented article form the basis for the design and construction of reliable foundations of buildings and transport facilities in regions with the spread of permafrost soils.