Abstract

Pile foundations are frequently employed in permafrost regions to support various infrastructure systems due to their robust load-bearing capabilities in frozen soils. However, these foundations are susceptible to diminished bearing capacity and higher displacements when subjected to warmer temperatures in permafrost areas. This paper introduces a research initiative aimed at devising a retrofitting method to increase the load carrying capacity of steel pile foundations in thawing permafrost regions. The primary objective was to re-establish frozen conditions in the thawed soil surrounding pile foundations and foster adfreeze bonding at the interface between the pile and the soil. The proposed refrigeration technique entails circulating a low-temperature freezing liquid (Antifreeze) within steel pile tubes to explore the feasibility of reducing the temperature of both the pile and its adjacent soil. Ideally, this process would induce freezing at the pile-soil interface, thus enhancing the load-bearing capacity of pile foundations in warming permafrost regions. A model pile load test setup was devised, employing steel pipe piles embedded in cohesionless, ice-poor soils, to investigate the potential formation of adfreeze bonding induced by the circulation of freezing liquid within the pile. Experimental findings demonstrated that localized freezing effectively reduced the temperature of the pile and its surrounding soil and facilitated the development of adfreeze bonding at the pile-soil interface. Remarkably, exposure to circulation of antifreeze liquid for just 25 minutes led to a substantial increase in the pile shaft capacity, doubling its initial strength.

Keywords:Pile foundations; Frozen ground; Adfreeze strength; Permafrost; Global warming