Long-term axial performance of continuous-flight pile in frozen soil

A number of buildings in the Canadian Arctic communities have failed or showed signs of failure of pile foundations caused by climate-change-induced excessive settlements. Effects of climate change warrant alternative pile types and new installation methods. Installing a pile into frozen soils by the torque method is rare in current practice of the Canadian Arctic. The continuous-flight pile is a new foundation type that is installed by torque. This study is aimed at investigating the axial load transfer of continuous-flight piles in frozen soils under long-term loads. A primary objective is to examine the effects of soil temperature, water content, and soil salinity on the resistance and the failure mode of continuous-flight piles in frozen soils. A series of axial load tests of model continuous-flight piles with a shaft diameter of 89 mm were carried out in the lab. Results show that primary and secondary creeps were observed during the constant load tests. The cylindrical shear mode and individual bearing mode were observed and inferred from the measured data. The adfreeze shear resistance and the individual plate bearing resistance under constant loads were estimated and verified using data from the literature. The adfreeze resistance increased with the applied load, and the plate bearing resistance increased as the normalized pile displacement rate increased. The mobilized adfreeze and plate bearing resistances suggest a potential increased load capacity of the continuous-flight pile compared to conventional smooth piles of similar diameter.