Effect of Degree of Saturation on Behavior of Helical Piles in Frozen Soils

This study focuses on the investigation of adfreeze strength and pullout capacity of helical piles in frozen unsaturated soils. The adfreeze strength plays an important role in capacity of helical piles especially for piles installed in frozen soils, and it depends on hydraulic and thermal conditions, including degree of ice saturation and temperature. An experimental investigation is performed in this study to quantify the impact of initial degree of saturation and changing thermal conditions on the adfreeze strength and pullout capacity. A physical modeling of a single helix pile is conducted in an unsaturated silt layer prepared at four different initial degrees of saturation. The pull-out tests are conducted on modeled piles to measure load-displacement curves at three different temperatures for each degree of saturation. Helical pile capacities are calculated, and adfreeze strengths are predicted from load-displacement curves. The results indicate a significant reduction in adfreeze strength of the pile-soil interface with increasing temperatures and decreasing degrees of saturation.