Permafrost heat pipe technology has been widely applied in cold-region engineering projects around the world since the mid-20th century, serving as an effective solution to problems such as thaw settlement and foundation instability in perennially frozen ground. The earliest and most representative application is the Trans-Alaska Pipeline, which stretches over 1,200 kilometers. Along this route, approximately 112,000 ammonia-carbon steel heat pipes were installed to prevent heat from the pipeline from transferring into the ground, thereby avoiding permafrost thaw and foundation subsidence. Operational tests have shown that these heat pipes can rapidly lower the temperature of pile walls and the permafrost at depths of up to six meters, keeping it below 0°C even during summer, ensuring long-term pipeline stability.

The working principle is as follows: during cold seasons, heat from the soil is transferred through the heat pipe to the air, cooling and freezing the soil to enhance foundation stability. In warm seasons, the heat pipe automatically stops operating, preventing heat from flowing back and preserving the "cold storage" effect. Typically, these heat pipes use a carbon steel/ammonia configuration, as ammonia exhibits favorable thermophysical properties at low temperatures and is chemically compatible with carbon steel. A common design features a diameter of 89 mm, wall thickness of 6 mm, total length of 7 m, and burial depth of 5 m, with finned condenser sections to enhance heat dissipation. Key manufacturing steps include ensuring ammonia purity, corrosion protection, vacuum preparation, and thermal performance testing. Beyond railways, this technology is also applicable to highways, bridges, and transmission towers in permafrost regions. Research methods include field temperature monitoring and numerical simulation, using unsteady-state thermal models to predict soil temperature field variations, optimize heat pipe design, and improve the long-term stability and safety of infrastructure in permafrost areas.