Development and Performance of an Adaptive Adfreeze Pile

Abstract

Field studies and geothermal modelling shows ground cooling below raised buildings in permafrost regions significantly offsets the ground warming impact of climate warming. For an adfreeze pile, the ground cooling below a raised building improves the capacity relative to pre-construction conditions. Many designers do not take credit for this cooling effect but propose to incorporate thermal mitigation in the design, such as the use of thermopiles. The adaptive adfreeze pile is an innovative concept that accounts for long-term cooling beneath raised buildings and the resulting enhanced pile capacity. The concept entails the installation of a closed ended steel pipe as a conventional adfreeze pile. If future ground temperatures warm above a design threshold, a small diameter thermosyphon could be inserted into the interior of the hollow pile. The retrofitted thermosyphon, if ever required, would passively cool the ground during winter to reduce the mean annual ground temperature and maintain pile capacity. This approach is cost-effective compared to conventional thermopile design and provides greater thermosyphon performance assurances in the long-term. This paper details of the application of this pile design for two, multi-story buildings in Old Crow Yukon, and describes the geothermal background showing its technical feasibility and initial performance data.