Pore–Water Salinity Effect on the Compression and Hydraulic Characteristics of Saturated Saline Soils

Changes in the pore-water environment have an obvious effect on the physical and mechanical properties of soil. Traditional consolidation theory has not considered the influence of the hydrochemical environment on the mechanical properties of soil. In order to investigate the mechanism of chemical action on geotechnical properties, in this study, one-dimensional compression tests and scanning electron microscope tests are carried out on soils prepared with different concentrations of NaCl solution. The mechanical characteristics reveal that the compression index shows a gradual decrease with an increase in pore-water salinity, and the structural yield stress of the soil increases gradually with the increase in pore-water salinity, reaching a maximum value of 50.34 kPa with a salt content of 5%. Conversely, the change in osmotic suction has minimal impact on the rebound index. Notably, the pore-water salinity primarily affects the intrinsic compression behavior of soft clays, as evidenced by an increase in the slopes of the sedimentary compression curve before yielding higher pore-water salinity. Combined with the analysis of microscopic test results, it is found that as the osmotic suction increases and the interparticle hydration capacity decreases, the soil particles change from a dispersed state to an aggregate state, leading to an increase in mesopores, and this increase indicates that the ability of the soils to resist the external loads also increases, which means an enhancement of the structural characteristic. In addition, the coefficient of permeability of the soil decreases as the consolidation pressure increases. Chemical consolidation produced by the increase in pore salt solution concentration causes a decrease in pore ratio, resulting in a smaller coefficient of permeability, and there exists a critical value for the effect of salt on the coefficient of permeability of the soil, which is related to the structural yield stress of the soil. This research provides a theoretical basis for the settlement prediction and the safety evaluation of soft ground in coastal areas.