Solute ions migrate

collide with and associate with both free water and bound water

indicating a virtual semi-permeable membrane effect in pore water. Electrostatic attraction draws some mobile ions into bound water

converting them into immobile ions. Spatially nonuniform ion distribution creates a chemical potential in pore water

causing a discrepancy between the actual pore-water pressure and its measured value in unsaturated saline soil. Therefore

the effective osmotic suction is used to characterize the chemical factors to describe the mechanical behavior of unsaturated saline soil. By clarifying the types and characteristics of pore water and ions in soil

considering the non-movable ions in liquid water

the calculation method of effective osmotic suction is determined by a representative elementary volume (REV). The contribution of chemical potential in pore water to Gibbs free energy of gas-liquid interface is analyzed. Based on soil-skeleton stress-balance analysis and the fact that the surface tension of the gas–liquid interface satisfies the Young–Laplace equation

we propose a generalized effective-stress equation for unsaturated saline soil that accounts for capillary and physicochemical effects. For loess with varying salinity and matric suction

isotropic compression and shear tests under controlled suction were conducted using an unsaturated true-triaxial apparatus. The relationship between the effective stress and isotropic deformation

the shear strength under different intermediate principal stress parameters of the saline loess is obtained

and the accuracy of the generalized effective stress equation is verified.