Effect of Na₂SO₄ Solution on the Compression and Microscopic Properties of Coastal Soft Soil

To investigate the impact of water chemistry on the mechanical properties of coastal soft soil, one-dimensional consolidation tests and scanning electron microscope analyses were conducted on unsaturated soil samples subjected to varying concentrations of Na₂SO₄ pore water and different salinity levels. The results show that: With the increase of salt content, the yield stress of coastal soft soil structure decreases by 9.5%, the compression index increases linearly, and the permeability coefficient increases; When the salt content is greater than 4%, the precipitated mirabilite crystals exist between the particle pores, and the soil skeleton effect is obvious, which leads to the increase of the yield stress of the soil structure and the decrease of the compression index and permeability coefficient. SEM images show that the average particle size of coastal soft soil increass with the increase of Na₂SO₄ solution concentration, and the flocculation structure soil particles increased. In addition, the structural parameters of coastal soft soil considering the concentration of salt content and consolidation pressure are established. The results show that the structural parameters decrease with the increase of consolidation pressure; When the consolidation pressure is less than the structural yield stress, the structural parameters first decrease and then increase with the increase of pore salt content, but when the consolidation pressure is greater than the structural yield stress, the structural parameters do not change significantly with the increase of salt content.