In engineering practice, unsaturated compacted loess is often utilized as a filling material in the loess regions. The loess inevitably undergoes one-dimensional compressibility and creep deformation due to the long-term effects of the upper soil layers and buildings. When the deformation is large enough, it tends to damage buildings and threaten engineering safety. In this regard, the one-dimensional compressibility and creep properties of unsaturated compacted loess based on incremental loading (IL) and constant rate of strain (CRS) methods have been studied. First, soil materials with an initial moisture content of 15% were prepared and then compacted into soil samples with an 80 mm diameter and a 10 mm height. Second, the compressibility and creep properties of the compacted loess samples obtained via the IL and CRS compression tests were compared and analyzed. In this study, several parameters, including the primary compression index C_c and secondary compression index C_α, were derived. Meanwhile, the moisture content of the samples was measured via electrical resistivity methods. Finally, the microstructural characteristics were derived via nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM) tests. The results showed that C_c and C_α increased with the increase in moisture content and vertical stress; C_α/C_c ranged from 0.026 to 0.042. Compared with the compression parameters and deformation of the samples, those obtained via the CRS tests are a little larger than those obtained via the IL tests for a given loading and initial moisture content. The electrical resistivity depends on pore water-connected channels, which were deeply affected by the initial moisture content, vertical stress and loading duration (or strain rate). Moreover, as vertical stress increased, the pore size and pore area gradually decreased, the coarse particles were broken, and the fine particles increased. The contacts between particles changed from point-to-point contacts and edge-to-edge contacts to face-to-face contacts. Meanwhile, as vertical stress and loading rate increased, the loess particles were apt to vary from irregular elongated particles to equiaxial circular particles. This investigation can provide a theoretical base and experimental support for improving ground stability and preventing landslide disasters in loess regions.

Owing to the alternating processes of rainfall and evaporation, the compacted loess employed in ground and roadbed construction frequently experiences drying and wetting (D-W) cycles. These cycles are prone to induce substantial deformation of the soil mass, posing a risk to the integrity of buildings and infrastructure. Consequently, this study delved into the effects of D-W cycles on the deformation behavior of compacted loess, considering varying initial dry densities and water contents. To achieve a profound understanding of the deformation characteristics of the compacted loess, we meticulously monitored the resistivity ratio, crack ratio, and microstructure throughout the tests. Furthermore, a constitutive model was developed to forecast the deformation of compacted loess under D-W cycles. The findings revealed that both the vertical strain and crack ratio exhibited an upward trend with the increase in D-W cycle numbers, while they exhibited a downward trend as dry density increased. Notably, water content was identified as a significant factor affecting both the crack ratio and resistivity ratio. Additionally, the occurrence and progression of D-W cycles and cracks led to a slight increase in particle abundance and the proportion of total pore area. Meanwhile, during the wetting process, the infiltration of water softened the cementing substances, resulting in a disruption of the connections between aggregates. This made it much easier for cracks in the soil to expand after the sample dried. The constitutive model was meticulously constructed by incorporating yield surfaces that account for decreasing and increasing water contents. The validity of the proposed model was substantiated through a comparative analysis of the measured and calculated data. This comprehensive investigation furnishes a theoretical foundation for assessing the stability of compacted loess ground and roadbeds subjected to D-W cycles.