Characterization of Adfreeze Shear Behavior at the Interface of Frozen Clay Till and Steel Piles

Frost heave of frost-susceptible soils in the active layer can produce uplift forces that can jack up pile foundations. One source of these uplift forces is the adfreeze stress that develops along the pile shaft. More accurate adfreeze stress values (both adfreeze shear strength and residual adfreeze stress) must be determined to properly consider them in pile design. This research utilized the direct shear test to characterize adfreeze stresses at frozen clay till and steel pile interface. The impacts of temperature, initial water content, and shear rate on adfreeze stresses were also evaluated. Both temperature and initial water content significantly affect adfreeze shear strength but have minimal impact on residual adfreeze stress. In contrast, the shear rate has a considerable impact on both. A wide range of adfreeze shear strength values were measured, ranging from 40 to 400 kPa, while residual adfreeze stresses are significantly lower, ranging from 15 to 60 kPa.