Influence of dry-wet cycles on hydraulic conductivity and microstructure of saline undisturbed loess with sodium sulfate

Triaxial permeability and CT tests during dry-wet cycles were performed to study hydraulic conductivity and microstructure of saline undisturbed loess with sodium sulfate. The results show that hydraulic conductivity increases with growing number of dry-wet cycle while the increasing rate decreases. Hydraulic conductivity exhibits a linear growth rate at higher mass fractions of sodium sulfate. In addition, hydraulic conductivity decreases at higher confining pressure and its attenuation rate also decreases. The significant similarities between surface crack morphology of 3D reconstruction model and that of soil samples show the reasonability of the 3D reconstruction technique. The increasing dry-wet cycles and higher salt content cause the formation of significant cracks, propagation of original cracks, and evolution and convergence of cracks to the center from around the surface of samples. Equation of the porosity for 3D reconstruction model after dry-wet cycles is established, which can well describe the variation of porosity quantitatively. Both microscopic porosity of 3D reconstruction model and macroscopic hydraulic conductivity exhibit the same variation, indicating that the porosity exactly can reveal the microscopic mechanism of hydraulic conductivity. © 2021, Central South University Press. All right reserved.