Why ground temperature matters
Permafrost can lose bearing capacity when ice within the soil thaws. Heat from a building, hot pipeline or industrial pad changes the thermal regime of its foundation. Passive cooling may help preserve frozen ground, but it cannot replace geotechnical investigation, foundation calculations or monitoring.
How a two-phase thermosiphon works
A sealed ground thermosiphon contains a working fluid. When outdoor air is colder than the soil, heat absorbed by its underground evaporator vaporises the fluid. Vapour moves to the finned condenser above ground, releases heat to the air and returns as liquid under gravity. This cycle needs no compressor or external electrical power.
What happens during summer
A conventional passive thermosiphon transfers little heat when outdoor air becomes warmer than the ground. It therefore does not provide active year-round refrigeration. The winter cooling effect must be sufficient to maintain the required ground temperatures through the warm season; this is determined by thermal modelling.
Typical applications
Such systems are used beside pile foundations and near industrial facilities, tanks and pipelines built on frozen ground. The number, depth, spacing and geometry of devices depend on soil stratigraphy, groundwater, climate, snow cover and the structure’s heat input. A universal installation spacing does not exist.
Selection, installation and monitoring
Check the calculated cooling capacity, working-temperature range, casing integrity, installation geometry and accessibility of the condenser. Soil thermometers or monitoring boreholes are needed to verify the actual temperature regime. A cold-looking condenser alone does not prove that the foundation remains within design limits.
Engineering standards
SP 25.13330.2020 covers foundations on permafrost soils; Amendment No. 3 has been in force since 14 June 2026 and updates provisions on cooling devices and geotechnical monitoring. Apply the current text, geological survey results, thermal model and the manufacturer’s documentation rather than relying on the device illustration.
Checklist for an enquiry
Provide the site location, ground-temperature measurements, borehole log, foundation layout, heat sources, expected service life, operating conditions and monitoring requirements. Ask the designer to check performance under both present and projected climate conditions.
Verified standards and scope
Sources are official Rosstandart registry entries. Verify the current amendments and applicability to the particular project and jurisdiction.
Frequently asked questions
Principle and application?
Design and selection?
Can the illustration be used as an installation drawing?
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