Experimental study on Atterberg limits and shear strength properties of saline clay based on microscopic pore characteristics

In this paper, the effect of salt (Na₂SO₄, NaCl) on the clay Atterberg limits and shear strength is revealed by using volumetric flask test and triaxial shear test, and the macroscopic mechanical performance results of the Atterberg limits and triaxial shear test reveal the mechanism of salt solution’s effect on the evolution of the deterioration of the microscopic pore structure of the soil body based on the perspective of microscopic pore characterization by using nuclear magnetic resonance (NMR) scanning and scanning electron microscopy (SEM) techniques. The results show that in Na₂SO₄ solution and NaCl solution, the decrease of double layer thickness and the increase of PH value caused by the increase of cation concentration are the main reasons for the gradual decrease of soil Atterberg limits, adsorbed bound water (ABW) content and shear strength. In addition, when the cation concentration is the same, \(\text{SO}_{4}^{2-}\) has a greater barrier effect like semi-permeable film than Cl⁻, which makes the double layer thickness of Na₂SO₄ solution thinner than NaCl solution, the Atterberg limits and ABW content is further reduced; Meanwhile, \(\text{SO}_{4}^{2-}\) has greater intergranular repulsion on the particle surface compared to Cl⁻, forming a larger pore structure further deteriorating the soil structure and reducing the soil shear strength. It provides more support for studying the effect of salt on the physical and mechanical properties of clay.