Abstract: To investigate the variation in pore distribution of remodeled weakly expansive soil at different dry densities, specimens with dry densities of 1.40, 1.50, 1.60, 1.70, 1.80 g/cm³ were prepared using a press sample machine. The pore structure and distribution characteristics of these specimens were analyzed through mercury-injection and saturation-permeability tests. The hydraulic tortuosity of the specimens were calculated based on mercury piezometric and saturation permeability tests. The results indicate a consistent pattern in the process of mercury entering and exiting specimens of varying dry densities. Due to distinct entry and exit paths and the presence of bottleneck pores, the mercury retains within the specimens. Furthermore, an increase in dry density results in a reduction in both pore volume and the quantity of large pores. The soil's pore structure becomes more intricate with higher dry densities, exhibiting a negative correlation between average pore diameter, porosity, total pore volume, and fractal dimension. Based on the experimental outcomes, saturated permeability coefficients and hydraulic tortuosity at varied dry densities were computed, revealing that the increase in hydraulic tortuosity with higher dry density lies in the changes in pore size and structure, consequently affecting the fluid's permeation ability within the soil.

Key words: expansive soil, mercury piezometric method, microstructure, saturated permeability coefficient, hydraulic tortuosity