Climate change brought about significant freeze–thaw (FT) deformation of clayey soils distributed in cold regions, which resulted from soil structure evolution including pore size distribution change and crack development. However, the formation of clay aggregate that dominates the soil deformation behavior during FT remains unclear. This study investigated the effects of clay contents (5 %, 10 %, 15 %, and 20 %) and subfreezing temperatures (−5 °C, −10 °C, and −15 °C) on the soil FT deformation properties by isotropic isothermal FT tests. Meanwhile, the soil structure evolution was characterized via Nuclear Magnetic Resonance and X-ray Computed Tomography. The results indicated that the frost heave ratio () and thaw settlement coefficient () non-linearly varied with clay content and subfreezing temperature. Specifically, the minimum and were observed in the specimen with 10 % clay content, and the maximum and were identified at −10 °C. This phenomenon can be attributed to the clay aggregate forming bimodal or unimodal pore size distribution (PSD) with different initial clay contents. The freezing characteristics of inter- and intra-aggregate pore water were determined by the solid-water interaction. Moreover, the FT action altered the structure of clayey soil by the change in PSD and the generation of cracks. The contribution of pore size change and crack development to the total volume change before and after FT was quantitatively analyzed. It demonstrated that pore size change was more important for the total volume change in specimens with lower clay content and higher subfreezing temperature, whereas crack development mainly contributed to the total volume change in the rest of the specimens. This study provides a deep insight into the deformation characteristics of clayey soils under different climate conditions in cold regions.

中文翻译：

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黏土含量和冰点以下温度对黏土冻融变形特性的影响

气候变化导致分布在寒冷地区的粘土发生显着的冻融变形，这是由于土壤结构演化，包括孔径分布变化和裂缝发育造成的。然而，在 FT 过程中主导土壤变形行为的粘土团聚体的形成仍不清楚。本研究通过各向同性研究了粘土含量（5 %、10 %、15 % 和 20 %）和冰点以下温度（−5 °C、−10 °C 和−15 °C）对土壤 FT 变形特性的影响。等温 FT 测试。同时，通过核磁共振和X射线计算机断层扫描对土壤结构演化进行了表征。结果表明，冻胀比（）和融沉系数（）随粘土含量和冰点以下温度呈非线性变化。具体而言，在粘土含量为 10% 的样品中观察到最小值 和 ，在 -10 °C 时确定最大值 和 。这种现象可归因于粘土骨料形成具有不同初始粘土含量的双峰或单峰孔径分布（PSD）。骨料间和骨料内孔隙水的冻结特性由固水相互作用决定。此外，FT作用通过PSD的变化和裂缝的产生改变了粘土的结构。定量分析了 FT 前后孔径变化和裂纹发展对总体积变化的贡献。结果表明，在粘土含量较低和低于冰点温度较高的样品中，孔径变化对总体积变化更为重要，而裂纹的发展主要对其余样品的总体积变化产生影响。该研究深入了解了寒冷地区不同气候条件下粘性土的变形特征。