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Research of operating conditions for soil thermal stabilization devices taking into account the impact of technical facilities on permafrost soils

UDK: 05.23.02
DOI: 10.24887/0028-2448-2017-8-116-119
Key words: permafrost soil, soil thermal stabilizer, cooling capacity of soil thermal stabilizer, thermal imaging survey, thermometric measurements of soil temperature
Authors: V.I. Surikov, A.A. Korotkov, E.A. Melnikova (The Pipeline Transport Institute LLC, RF, Moscow)

The strength and load-carrying capacity of frozen rocks is much higher than that of the same rocks in the thawed state. The strength of frozen rocks is determined by the interaction between mineral particles and ice crystals, i.e. ice cement bonds. This type of bond significantly exceeds the cohesion of particles in the thawed rock and intensifies with decreasing temperature. For the entire period of construction and operation of technical facilities, there should be provided for a set of measures to ensure and maintain the specified temperature of frozen soils, as well as the required load-carrying capacity. To ensure the specified temperature of the soils, the installation of seasonal-acting cooling devices - soil thermal stabilizers in the base of industrial and civil objects is widely used. Thermophysical properties of frozen rocks can vary with time, as they depend on the amount of unfrozen water, the density of the rock skeleton, humidity, including as a result of technogenic impact. Therefore, when operating technical objects, the actual temperature of the soils and the cooling capacity of the soil thermal stabilizers are monitored. At checking the operating conditions of the soil thermal stabilizers and analyzing the results of measurements of soil temperature, there are cases when soil thermal stabilizers operate with an increased cooling capacity. This indicates the insufficient effectiveness of measures to ensure the specified soil temperature for actual operating conditions. One of the reasons is the difference between the actual climatic conditions and those taken during the design. The article presents an analysis of the results of meteorological observations indicating changes in climatic conditions at sites located in the Far North, as well as the results of a numerical assessment of the effect of climatic conditions on the effectiveness of measures for temperature stabilization of soils. To assess the effectiveness of the soil thermal stabilizers action, mathematical models have been developed, with the use of which the calculations of the cooling capacity under various climatic conditions have been performed. Based on the developed models, calculations of the compensating measures necessary to ensure the required temperature regime of the soils were carried out.

References

1. Ivanitskaya E.V., Monitoring of Trans-Alaska pipeline system (In Russ.), Nauka i tekhnologii truboprovodnogo transporta nefti i nefteproduktov, 2011, no. 1 (1), pp. 96–101.

2. Lisin Yu.V., Sapsay A.N., Surikov V.I. et al., Stablishment and implementation of innovative construction technologies in the development projects of the oil pipeline system in Western Siberia (projects «Purpe – Samotlor», «Zapolyarye – Purpe») (In Russ.), Nauka i tekhnologii truboprovodnogo transporta nefti i nefteproduktov, 2013, no. 4 (12), pp. 6–11.

3. Sapsay A.N., Soshchenko A.E., Mikheev Yu.B. et al., Design solutions for the soil thermo-stabilizers and evaluation of their efficiency for providing hard frozen soil condition of foundation basis in the case of above-ground routing (In Russ.), Nauka i tekhnologii truboprovodnogo transporta nefti i nefteproduktov, 2014, no. 1 (13), pp. 36–41.

The strength and load-carrying capacity of frozen rocks is much higher than that of the same rocks in the thawed state. The strength of frozen rocks is determined by the interaction between mineral particles and ice crystals, i.e. ice cement bonds. This type of bond significantly exceeds the cohesion of particles in the thawed rock and intensifies with decreasing temperature. For the entire period of construction and operation of technical facilities, there should be provided for a set of measures to ensure and maintain the specified temperature of frozen soils, as well as the required load-carrying capacity. To ensure the specified temperature of the soils, the installation of seasonal-acting cooling devices - soil thermal stabilizers in the base of industrial and civil objects is widely used. Thermophysical properties of frozen rocks can vary with time, as they depend on the amount of unfrozen water, the density of the rock skeleton, humidity, including as a result of technogenic impact. Therefore, when operating technical objects, the actual temperature of the soils and the cooling capacity of the soil thermal stabilizers are monitored. At checking the operating conditions of the soil thermal stabilizers and analyzing the results of measurements of soil temperature, there are cases when soil thermal stabilizers operate with an increased cooling capacity. This indicates the insufficient effectiveness of measures to ensure the specified soil temperature for actual operating conditions. One of the reasons is the difference between the actual climatic conditions and those taken during the design. The article presents an analysis of the results of meteorological observations indicating changes in climatic conditions at sites located in the Far North, as well as the results of a numerical assessment of the effect of climatic conditions on the effectiveness of measures for temperature stabilization of soils. To assess the effectiveness of the soil thermal stabilizers action, mathematical models have been developed, with the use of which the calculations of the cooling capacity under various climatic conditions have been performed. Based on the developed models, calculations of the compensating measures necessary to ensure the required temperature regime of the soils were carried out.

References

1. Ivanitskaya E.V., Monitoring of Trans-Alaska pipeline system (In Russ.), Nauka i tekhnologii truboprovodnogo transporta nefti i nefteproduktov, 2011, no. 1 (1), pp. 96–101.

2. Lisin Yu.V., Sapsay A.N., Surikov V.I. et al., Stablishment and implementation of innovative construction technologies in the development projects of the oil pipeline system in Western Siberia (projects «Purpe – Samotlor», «Zapolyarye – Purpe») (In Russ.), Nauka i tekhnologii truboprovodnogo transporta nefti i nefteproduktov, 2013, no. 4 (12), pp. 6–11.

3. Sapsay A.N., Soshchenko A.E., Mikheev Yu.B. et al., Design solutions for the soil thermo-stabilizers and evaluation of their efficiency for providing hard frozen soil condition of foundation basis in the case of above-ground routing (In Russ.), Nauka i tekhnologii truboprovodnogo transporta nefti i nefteproduktov, 2014, no. 1 (13), pp. 36–41.


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