Research on Wetting-Deformation Regularity and Microstructure Evolution Characteristics of Remoulded Loess in Triaxial Soaking Tests

To explore the wetting-deformation regularity and microstructure evolution characteristics of filled soil, three groups, 17 samples, of immersed anisotropic consolidation tests of reshaped Q₂ loess in the Yan’an new district were studied using the improved unsaturated soil triaxial apparatus with computed tomography （CT）. The CT scanning was applied to the two sections of the samples in the triaxial soaking studies. The macroscopic deformations, soil samples’internal mesoscopic structure evolution CT images and the corresponding CT data were obtained in the consolidation and the wet process of the soil sample. Structural parameters and structural evolution variables of the soil were defined based on the CT data. The results show that the dry density, net confining pressure, matrix suction, and deviatoric stress have a significant influence on the wetting deformation characteristics. Increased dry density can effectively reduce the wetting deformations and the risk of wet shear failure. （The strains of the dry density specimen at 1.52 g/cm³ and 1.69 g/cm³ during immersion were –0.58% to 4.66% and –0.58% to 2.43%, respectively, and the strain of the dry density specimen of 1.79 g/cm ³ was 0.019%.）The CT data of all samples increased, indicating that the specimens become more and more compacted due to humidification deformation. In the early stage of immersion, the original structures of the soil samples were destroyed, and the change of CT data was more severe, reaching 60% of the total change. Meanwhile, the result is affected by the dry density, net confining pressure, suction, deviatoric stress, and moisture content. These results are valuable for the design of filled soil engineering and provide a scientific basis to establish the structure of the unsaturated remoulded loess damage evolution equation and the structural model.