Coupled Hydromechanical Behavior of Compacted Loess during Isotropic Compression

Abstract Compacted loess is a special collapsible unsaturated soil and is sensitive to hydraulic conditions. Understanding and modeling the coupled hydromechanical behavior of compacted loess during isotropic compression is essential for establishing a complete constitutive model for unsaturated soils, which is of significance for predicting the deformation of loess fills in engineering. In this research, a series of constant suction isotropic compression tests are conducted to study the behavior of compacted loess. The experimental results show that volume change and soil–water characteristics are mutually affected during compression and that the normal compression curves flatten out and shift downward with the decrease in suction. Based on the experimental observations, the normal compression surface is modified, and the loading–collapse yield curve is deduced for the compacted loess. An equation associated with the void ratio is used to describe the effect of the volume change on the soil–water characteristics. Furthermore, a coupled hydromechanical constitutive model for the compacted loess under isotropic compression conditions is proposed within the framework of the Barcelona basic model. Model predictions of the mechanical and hydraulic behaviors of the compacted loess for constant suction isotropic compression tests and wetting tests at constant net stresses are compared with experimental data to verify the performance and validation of the proposed model. The comparisons indicate that the proposed model can accurately reproduce the coupled hydromechanical behavior of the compacted loess under isotropic compression conditions.