Improvement of Pile Load Capacity in Warm Frozen Soils

Adfreeze piles have been widely used to transfer the structural loads to the ground in permafrost region mainly due to their high load carrying capacity in frozen ground. These foundations are often designed based on the strength characteristics of frozen ground materials and the adfreeze bond at the pile–soil interface. However, pile foundations located in frozen grounds may experience significant reduction in their load carrying capacity when exposed to higher ambient temperature. This paper attempts to examine the possibility of circulating a freezing liquid within and around existing pile foundations to maintain the frozen state of pile–soil adfreeze bonding around the piles. A model pile load test setup was developed using steel pipe piles embedded in cohesionless ice-poor soils to examine the possibility of adfreeze bond formation induced by circulation of freezing liquid in the pile. The experimental results showed that local freezing is capable of decreasing temperature in the pile surrounding soil and developing adfreeze bond at the pile–soil interface. The pile shaft capacity significantly increased up to twice its initial strength when the pile was exposed to circulation of antifreeze liquid for only 25 min. A finite element model was also developed using ABAQUS software and calibrated by the test results to investigate the effect of controlling parameters on load carrying capacity of the piles.