An important source of time-dependent pile deformation is creep behavior at pile-frozen soil interface in permafrost regions. A creep model for pile-frozen soil/ice interfaces was proposed based on a series of multistage creep tests. The test results show that the creep behavior of the pile-frozen soil/ice interfaces is easily observed at a steady rate larger than 0 even at a small load level, which increases as the increase of load level. The elastic shear modulus increases at a slowing down rate with the increase of load level. The interfaces are mainly strengthened during the creep process until the occurrence of the accelerating creep, which is more obvious for frozen soil. A large amount of ice in frozen soil can enhance the creep rate and reduce the carrying capacity of pile foundation. The viscosity [Formula: see text] reflecting steady creep rate, the instantaneous shear modulus [Formula: see text], and the critical stress [Formula: see text] required for describing damage behaviors distribute in the form of Bigaussian asymmetric peak function with ice content. The Burger model considering ice effect and damage effect is feasible to describe the entire creep behavior of the interfaces. Sensitivity analysis reveals that ice content in frozen soil has a marked influence on pile deformation, a cooling method can probably adjust the creep deformation of pile in frozen soil with high ice content.

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Owing to a minor thermal disturbance to the permafrost environment, cast-in-place piles are widely used for building and bridge foundations in permafrost regions. However, because of the dynamic and cyclic variation in frozen ground affected by the atmosphere, the load transfer mechanism is not yet clear, and the current design is economically insufficient. To illustrate the bearing pattern of cast-in-place piles subjected to freeze-thaw cycles, a systematic in situ investigation was carried out.Results show that the load from the superstructure has a marginal action effect, while freeze-thaw cycles have a more significant action effect. Freeze-thaw cycles have a decisive effect on the dynamic variations of the pile's working state and action effect sharing while the mechanisms are quite different, which vary with depths. Action effect sharing of the pile shaft and tip experiences a cyclic variation and is affected by the long-term effect of freeze-thaw cycles. The shaft takes an increasing sharing proportion gradually and has a 19% rise after two freeze-thaw cycles, while the pile tip goes the opposite way. Two years after the building is completed, the bearing capacity is almost entirely provided by shaft resistance and mainly by the upper onethird of the pile. This research clarifies several essential issues about the bearing pattern and provides solid scientific support and novel opinions for the pile design in permafrost regions.