Field test study of a novel solar refrigeration pile in permafrost regions

Cast-in-place piles are popular foundation forms in permafrost regions. The freezing force at the pile-soil interface is the main source of bearing capacity, which is quite sensitive to ground temperature. The warming climate and engineering activities can cause the permafrost to thaw, affecting the long-term stability of the pile foundation. However, the method of cooling pile foundations is rarely reported. This paper proposes a solar refrigeration pile consisting of a solar power system, a compression refrigeration system, and a concrete pile to control the surrounding permafrost temperature. A field test was conducted in the Qinghai-Tibet Plateau permafrost regions to assess the actual cooling performance. The test results showed that the new pile effectively cooled the surrounding permafrost in the warm season without human intervention. After 10 days of cooling, the influence radius of the solar refrigeration pile exceeded 1 m. Furthermore, the solar refrigeration pile significantly improved the bearing capacity. This study provides a practical solution for addressing the challenge of maintaining the stability and bearing capacity of pile foundations in permafrost regions under the influence of climate change and human activities.