Saline soil is a widely distributed special soil with poor engineering properties. In seasonally frozen regions, the poor properties of saline soil will cause many types of engineering damage such as road boiling, melt sinking, and subgrade instability. These engineering failures are closely related to the shear strength of saline soil. However, there are relatively few studies on saline soil in cold regions. The strength of the soil is always determined by its microstructure; therefore, the study aims to investigate the relationship between the shear strength and microscopic pore structure of saline soil with different freeze–thaw cycles and salinities. The shear strength characteristics of saline soil with different salinities subjected to different freeze–thaw cycles were obtained by triaxial tests. In addition, the microstructure of the soil samples was investigated by scanning electron microscopy (SEM) tests, and the microscopic pore parameters of the soil samples, including porosity (N), average pore diameter (D¯), average shape coefficient (K), surface fluctuation fractal dimension (F), and orienting probability entropy (Hm), were obtained by image processing software quantitatively. Based on the experimental results, the influence of freeze–thaw cycles and salinity on the shear strength characteristics and microstructure of the soil samples were analyzed. Besides that, in order to effectively eliminate the collinearity between independent variables and obtain a stable and reasonable regression model, principal component regression (PCR) analysis was adopted to establish the relationship between the microscopic pore parameters and the failure strength of the soil samples. The fitting results demonstrated that the failure strength of saline soil is mainly related to the size and direction of the pores in the soil, and it has little correlation with pore shape. The failure strength of the soil was negatively correlated with the average pore diameter (D¯) and porosity (N), and it was positively correlated with the orienting probability entropy of the pores (Hm). This study may provide a quantitative basis for explaining the variation mechanism of the mechanical properties of saline soil from a microscopic perspective and provide references for the symmetry between the changes of the macroscopic properties and microscopic pore structure of the saline soil in cold regions.

中文翻译：

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不同冻融循环和盐度的盐渍土抗剪强度与微观孔隙参数的关系

盐渍土是一种分布广泛、工程性质较差的特殊土壤。在季节性冰冻地区，盐渍土的不良特性会导致道路沸腾、融化下沉和路基​​失稳等多种类型的工程破坏。这些工程故障与盐渍土的抗剪强度密切相关。但对寒冷地区盐渍土的研究相对较少。土壤的强度总是由其微观结构决定的；因此，本研究旨在研究不同冻融循环和盐度的盐渍土抗剪强度与微观孔隙结构之间的关系。通过三轴试验获得不同盐度盐渍土在不同冻融循环下的抗剪强度特性。此外，通过扫描电镜(SEM)测试对土样的微观结构进行了研究，土样的微观孔隙参数包括孔隙率(N)、平均孔径(D¯)、平均形状系数(K)、表面起伏分形维数（F）和定向概率熵（Hm）通过图像处理软件定量得到。根据试验结果，分析了冻融循环和盐度对土样抗剪强度特性和微观结构的影响。除此之外，为了有效消除自变量之间的共线性，得到稳定合理的回归模型，采用主成分回归（PCR）分析建立微观孔隙参数与土样破坏强度之间的关系。拟合结果表明，盐渍土的破坏强度主要与土壤中孔隙的大小和方向有关，与孔隙形状相关性不大。土的破坏强度与平均孔径（D¯）和孔隙率（N）呈负相关，与孔隙定向概率熵（Hm）呈正相关。