Hydromechanical and structural properties of compacted loess have a significant impact on the stability and reliability of subbase and subgrade, which needs to be quickly determined in the field and laboratory. Hence, an electrical resistivity method was used to characterize the hydromechanical and structural properties of compacted loess during constant rate of strain compression. In the present work, compacted loess samples with a dry density of 1.7 g/cm³, a diameter of 64 mm, a height of 10 mm and different water content ranging from 5–25% were prepared. The constant rate of strain (CRS) tests were conducted by a developed oedometer cell equipped with a pair of horizontal circular electrodes (diameter of 20 mm) and vertical rectangular electrodes (width of 3.5 mm) to determine the electrical resistivity of compacted loess. The results showed that as average water content increases, plastic compression indices increase from 0.220 to 0.350 and the elastic compression indices increase from 0.0152 to 0.030, but they decrease to 0.167 and 0.010 and yield stress decreases from 381.28 kPa to 72.35 kPa. Moreover, as vertical strain increases, the variation trend of average formation factor and average shape factor for the lower water content decreases but increases for the maximum water content, and the anisotropy index first decrease and then tend to increase slightly, which indicates that the structural properties of unsaturated and saturated samples during compression exhibits different trend and the anisotropy of samples tend to be stable as vertical strain increases. As the water content increases, the average formation factor and average shape factor decrease, but the anisotropy index first decreases then increases, suggesting that water content has a significant impact on these electrical indices. More important, The coefficients of average formation factor decrease from 33.830 to −1.698 and the coefficients of average shape factor decrease from 8.339 to −0.398 as water content increases, whereas there is less variation for the coefficient of anisotropic index with a value of 2.190. An equation correlating average formation factor and water content and vertical strain is regressed to characterize the hydromechanical properties of compacted loess by measuring its impedance, which can be used to evaluate the stability of compacted loessic ground and subgrade.

Coarse-grained soil is a common material for earth-rock dams and soft-ground projects. However, such soil particles are prone to breakage under load, thus affecting project safety. Accurately understanding the particle breakage characteristics is crucial to the safety design of related projects. Due to the scale effect, the indoor test results of scaled soil materials often fail to effectively reflect the breakage of coarse-grained soil particles with the original gradation. According to previous studies, the scale effect of scaled soil materials is mainly affected by the maximum particle diameter D_max and the gradation structure. Among them, the gradation structure can be represented by the gradation area S. By changing the gradation area S and the maximum particle diameter D_max, 39 coarse-grained soil specimens with the same relative compaction were prepared for loading tests on a large-scale triaxial coarse-grained soil test system. The indices B_w and B_g were developed to quantitatively analyze the scale effect’s influence on coarse-grained soil particle breakage, with a focus on identifying strategies to mitigate this scale effect. The test results show the following findings: Maintaining a constant maximum particle diameter, the indices B_w and B_g for particle breakage show a decrease as the gradation area enlarges, revealing a logarithmic correlation. Conversely, with a stable gradation area, these indices, B_w and B_g, rise as the maximum particle diameter increases, indicating an exponential relationship. The experimental findings led to the development of a scale effect-based calculation model for B_w and B_g using the similar gradation approach, whose accuracy has been confirmed. Furthermore, a prediction technique for the breakage degree of original-gradation coarse-grained soil under specific confining pressure was formulated using indoor test data, potentially enhancing project design safety. In the design of earth-rock dams, the research results can be used to more accurately predict the degree of particle breakage of coarse-grained soil with the original gradation. This can optimize the design of the dam body structure and improve the safety of the project.

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.