Adfreeze Strength and Creep Behavior of Pile Foundations in Warming Permafrost

Abstract

An experimental investigation was carried out to evaluate the thermal exposure effect on load carrying capacity and creep behavior of steel piles embedded in ice-poor frozen soils using steel-soil interface tests. The interface testing was conducted in a walk-in cold room to enable testing at various temperatures below the freezing point. A series of stress-displacement curves were established at different temperatures and under various normal stresses. The results showed a significant reduction in adfreeze strength of the pile-soil interface as the exposure surface temperature increased. The interface strength decreased approximately 300% when the exposure temperature increased from −1.5 °C to 0 °C. Such condition may be witnessed in warm permafrost that experience temperature ranging from −3 °C to 0 °C. The shear stress–strain curves showed a brittle behavior followed by significant loss of bearing capacity. Pile creep rate in ice-poor soils increased by about 60% when the interface was exposed to warming from −10 °C to −5 °C and showed tertiary creep when reaching −4 °C.