Thermal and mechanical characteristics of a thermal pile in permafrost regions

Abstract

Cast-in-place pile foundations are widely used in permafrost regions to support buildings. The stability of cast-in-place pile foundations is highly sensitive to permafrost thermal regime changes. Permafrost degradation caused by climate change is increasing the disaster risk of cast-in-place pile foundations. However, proactive cooling methods for cast-in-place pile foundations are seldom reported. The cold energy produced by two-phase closed thermosyphons (TPCTs) can efficiently prevent the permafrost thermal regime from being disturbed by engineering activities and climate change. TPCTs were installed in a concrete pile forming a thermal pile. Then, a model experiment was conducted to explore the thermal regime, influence scope, dissipation process of cold energy, and freezing strength of the thermal pile. The results indicated that the thermal pile may significantly cool the foundation soil. Most of cold energy produced by the thermal pile dissipated during the warm period, and the cooling scope of the thermal pile can cover the area within a 40 cm (twice the pile diameter) radius around the pile. Additionally, the TPCTs can significantly improve freezing strength between the thermal pile and frozen soil. The lesson learned from this study can provide a new approach to control the thermal regime of cast-in-place pile foundation in permafrost, which was of valuable to the construction of pile foundations in cold regions.

Keywords

• Pile foundation
• Cold energy
• Two-phase closed thermosyphon
• Freezing strength
• Permafrost regions