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.

Soil Freeze-Thaw and Water Transport Characteristics Under Different Vegetation Types in Seasonal Freeze-Thaw Areas of the Loess Plateau

“…The freezing and thawing characteristics of the areas in terms of soil freezing days, number of freezing and thawing cycles, freezing temperature, and freezing depth are quite distinct from the seasonal freezing and thawing characteristics in areas of the Loess Plateau. Similarly, several researchers currently use the 24-h average ST (daily average ST) as a statistical unit, and a daily average ST below 0°C as a basis for determining the occurrence of soil freezing (Guo et al, 2011;Guo et al, 2020). However, the statistical method is not suitable for determining seasonal freezing and thawing in areas of the Loess Plateau.…”

Hydrothermal Changes and Physicochemical Characteristics of Subtropical Subalpine Soils under Freezing and Thawing

“…The freezing-thawing characteristics of this region are different from those of permafrost regions [21]. Due to the specificity of alpine peat bog soils, soil water and heat transfer characteristics under seasonal freeze-thaw conditions are unclear [22]. For low-latitude subtropical alpine peat bog areas, the peat accumulation rate is high due to the low temperature and wet environment all year round, and the freeze-thaw cycle caused by the diurnal and seasonal temperature difference will change the soil hydrothermal process, which makes the peat soil release a large amount of CO 2 when melting, thus affecting the regional microclimate.…”