Thermal Stability Evaluation Method Based on Pile’s Bearing Capacity in a Permafrost Region

Abstract Pile foundations are widely adopted in the Qinghai–Tibet Railway. The pile’s bearing capacity must be influenced the trends of global warming, rising foundation soil temperatures, expanding active layers, ground ice melting, etc. Thus, the pile’s long-term bearing capacity must be understood, and methods for evaluating its stability in permafrost regions must be developed. The bearing capacity of a pile foundation in a permafrost region is caused by the freezing strength of the pile–soil interface and support force at the pile bottom. Based on the formation mechanism of the bearing capacity of pile foundations in permafrost regions, the stability ratio of the freezing area and the freezing strength between the pile and soil are proposed to evaluate the thermal stability of the pile’s bearing capacity in permafrost. Using the method, a bearing capacity study on a single pile in typical moist permafrost and two piles in a permafrost region where warm groundwater is underground is performed. Compared with the field-measured value, the evaluation method proves to be correct and effective. Using the two parameters dependent on the soil–pile interface temperature, the effect of the thermal stability of pile bearing capacity may be described intuitively. Thus, both parameters are conducive to the analysis of pile bearing capacity formation mechanism in permafrost.